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Pharmacology and Toxicology
Original Research Article
2023
:2;
7
doi:
10.25259/AJPPS_2023_007

Hepatoprotective effects of Allanblackia gabonensis aqueous trunk bark extract on carbon tetrachloride-induced chronic liver damage in Wistar rats

US Food and Drug Administration, Silver Spring, Maryland, United States
Department of Biological Sciences, Faculty of Science, University of Ngaoundere, Ngaoundere, Cameroon
Department of Animal Biology, Faculty of Science, University of Yaoundé I, Yaounde, Cameroon
Department of Psychology, Faculty of Letters and Human Social Sciences, University of Douala, Douala, Cameroon
Department of Organic Chemistry, Faculty of Science, University of Douala, Douala, Cameroon
Department of Animal Biology, Faculty of Science, University of Douala, Douala, Cameroon
Corresponding authors: Edwige Y. C. Vouffo, PharmD PhD US Food and Drug Administration, Silver Spring, Maryland, United States. Edwige.chiogovouffo@fda.hhs.gov Romeo J.G. Temdie, PhD Department of Biological Sciences, Faculty of Science, University of Ngaoundere, Ngaoundere, Cameroon. temdie2011@gmail.com
Licence
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-Share Alike 4.0 License, which allows others to remix, transform, and build upon the work non-commercially, as long as the author is credited and the new creations are licensed under the identical terms.

How to cite this article: Vouffo EYC, Temdie RG, Donfack MM, et al. Hepatoprotective effects of Allanblackia gabonensis aqueous trunk bark extract on carbon tetrachloride-induced chronic liver damage in Wistar rats. Am J Pharmacother Pharm Sci 2023;7.

Abstract

Objectives:

Natural bioactive compounds protect against oxidative stress-induced diseases. Studies have demonstrated antioxidant properties of Allanblackia gabonensis (member of Clusiaceae family), which is used for liver diseases. This work was designed to investigate the hepatoprotective effects of A. gabonensis aqueous trunk bark extract against carbon tetrachloride (CCl4)-induced chronic liver injury.

Materials and Methods:

Rats were divided into six groups of five rats each. Rats of control and CCl4 groups received distilled water orally from week 1 to week 12. A. gabonensis aqueous extract was given orally to preventive (PREV) test group (200 mg/kg) from week 1 to week 12. SIM group and two curative groups received silymarin 25 mg/kg and extract (100 or 200 mg/kg) from week 8 to week 12. CCl4 was injected hypodermically to induce chronic liver injury to all groups except control, 2 h after treatment, from week 1 to week 12. All rats were often weighed and were sacrificed 12 weeks later under anesthesia and blood was collected in ethylene diamine tetra-acetic acid tubes and plain tubes for hematological profiling and serum preparation, respectively. Liver and kidney functions were assessed by measuring alanine transaminase (ALT), aspartate aminotransferase (AST) serum activities, serum creatinine, total bilirubin, and total protein levels. Superoxide dismutase (SOD), catalase, glutathione (GSH), and malondialdehyde (MDA) were assessed. Histology of the liver and kidney was done.

Results:

Administration of CCl4 to rats resulted in significant (P < 0.05) impairment of the animals’ weight growth. ALT activity, creatinine, total bilirubin, and MDA levels were significantly increased. Total proteins, GSH levels, SOD, and catalase activities were decreased in the CCl4 group compared to control. PREV or curative administration of A. gabonensis extract (100 or 200 mg/kg) significantly reduced liver injury by preventing significant elevation of ALT activity, creatinine, and total bilirubin levels and exhibited significant reduction in the levels of MDA, compared to the CCl4-group. These effects of A. gabonensis extract were evident by a marked improvement of the liver and kidney histological architectures.

Conclusion:

The results revealed antioxidant and anti-inflammatory hepatoprotective effects of the aqueous extract of A. gabonensis and constituted a scientific basis for further research on this plant.

Keywords

Allanblackia gabonensis
hepatoprotective
rats
carbon tetrachloride
antioxidant

INTRODUCTION

Many xenobiotics enter the liver through portal vein after absorption.[1] Carbon tetrachloride (CCl4) was found to be one of the best characterized animal models of xenobiotic-induced oxidative stress-mediated liver toxicity.[2] CCl4 is the commonly used method to screen hepatoprotective activity of drugs.[1] Fouad et al.,[3] reported that the conversion of CCl4 by cytochrome P450 yields two free radicals trichloromethyl radical (˖CCl3) and peroxyltrichloromethyl radical (˖OOCCl3). The hepatotoxic effect of most chemicals is characterized by increased free radical production, increased tissue lipid peroxidation, transaminases, bilirubin, total cholesterol and triglycerides, and increased alkaline phosphatase activity.[4] It was reported that oxidative stress caused by the accumulation of reactive oxygen species in the liver is the primary pathogenic mechanism of chemical-induced liver injury.[5] The liver, whether in a human or a rodent, performs several functions that are crucial for life, such as drug metabolism, protein synthesis, detoxification, micronutrients storage, and cholesterol production.[6] It also contains diverse liver enzymes involved in the metabolism of drugs and chemicals. Oxidative stress is known to cause liver diseases and there are many liver enzymes with antioxidant potential to prevent or to stop the oxidative stress process and therefore improve the liver function.

Medicinal plants contain antioxidant compounds with an important hepatoprotective effect.[7] Among numerous medicinal plants, Allanblackia gabonensis which belongs to the Clusiaceae family, has been found to contain antioxidant compounds.[8,9] A. gabonensis is a sub-montane species, that is found above 500 m altitude above sea level.[10] This plant is largely used in traditional medicine to improve virility in men and to treat infection such as dysenteries, cold, and tooth ache.[11,12] Cameroonian population also uses it to relieve pain, rheumatism dysentery, toothache, and inflammations.[13] The previous reports showed its antimicrobial, antileishmanial and antibacterial,[13-15] analgesic and anti-inflammatory properties,[16] hepato-nephroprotective and antioxidant effects against acute acetaminophen-induced liver and kidney disorders in rats,[8] and anticancer activities.[17,18]

Phytochemical studies showed that the stem bark of A. gabonensis contains xanthone, benzophenone, flavonoid, and phytosterol.[14] Nganou et al.,[15] following a successive chromatography of the methanol stem bark extract of the A. gabonensis, have isolated a new polyprenylated benzophenone along with the known kaempferol, morelloflavone, morelloflavone 7-O-β-d-glucopyranoside, β-stosterol 3-O-β-d-glucopyranoside, and β-sitosterol. High-performance liquid chromatography confirmed the presence of 1,3,6,7-tetrahydroxy-2-(3-methylbut-2-enyl) xanthone, Allan xanthones A and D, some flavonoids, and phytosterols.[14,15] Based on the above information, and given that no studies have been done on chronic liver damage to our knowledge, we aimed to study the hepatoprotective effects of A. gabonensis aqueous trunk bark extract against CCl4-induced chronic liver damage in rats.

MATERIALS AND METHODS

Plant material

A. gabonensis trunk bark was collected in June 2007, from Kola mountain at Nkolbisson, Center region of Cameroon and identified at the National Herbarium of Cameroon, where a voucher specimen N° 23255/SRF/Cam was deposited.

Preparation of extract

The air-dried trunk bark was powdered, and 500 g of powder was extracted by decoction in distilled water (1.5 L) for 15 min. After filtration, the filtrate was concentrated in oven at 55°C to obtain brown residue of 41.5 g (8.3% yield), which was stored in the refrigerator (4°C) in a sealed labeled bottle for further study.

Animals

Three-month-old albino rats (30) of both sexes (15 males and 15 females), weighing 130–160 g, were used in this study to comply with the requirement of the experimental model of hepatotoxicity due to CCl4 that is suitable for rats. All rats were bred in animal house of the Department of Animal Biology and Physiology, University of Yaoundé I, Cameroon. Rats were housed in cages under standard laboratory conditions (12:12 light/dark cycle at 25 ± 8°C), with free access to the water and standard commercial diet. The experiment was conducted in accordance with the institutional guidelines approved by the National Ethics Committee of Cameroon (No. FWAIRD 0001954).

Experimental design

Assessment of the hepatoprotective activity of A. gabonensis aqueous extract was carried out following procedure described by Mu et al.[19] which was modified by including a preventive (PREV) group of rats to appreciate both PREV and curative effects.

Rats were divided into six groups of five animals each and they were fasted 12 h before the administration of different substances. The control group (group 1) received orally distilled water without any additional treatment from week 1 to week 12. The CCl4 group (group 2) and PREV group (group 3) were, respectively, given orally distilled water and a daily dose of A. gabonensis aqueous trunk bark extract (200 mg/kg) from week 1 to week 12. The Silymarin (SIM) group (group 4) and curative groups (group 5 and 6), respectively, received orally SIM (25 mg/kg) and plant extract (100 and 200 mg/kg) once daily, from week 8 to week 12. SIM is a hepatoprotective agent widely used to treat liver damage of various origins. The CCl4 dissolved in olive oil (50% solution) was injected hypodermically twice weekly to all groups except control to induce chronic liver injury, from the 1st week to the last week (12th week). The first administration of CCl4 was at a dose of 3 mL/kg and the following doses were at 2 mL/kg. All rats were weighed regularly during the experiment after 2 h of fasting and had free access to water and a standard commercial diet the rest of the time.

At the end of the treatment, 12 weeks later, all rats were sacrificed under anesthesia and blood was collected in ethylene diamine tetra-acetic acid tubes for hematological profiling, and in plain tubes for serum preparation by centrifugation (6000 rpm) for 20 min. The liver, kidney, and heart were dissected from the rats, rinsed in 0.9% sodium chloride and weighed. A sample of these organs was cold ground and homogenized in Tris-hydrochloride buffer (50 mM pH: 7.4) (liver and kidney) or in Mc Even (heart). The 20% homogenate obtained each time was centrifuged at 6000 rpm for 20 min at 4°C and the supernatant recovered. The serum and supernatant were stored at −20°C and used for biochemical analysis. Liver and kidney samples were processed for histological analysis.[20]

Measurement biochemical parameters

Alanine transaminase (ALT), aspartate transaminase (AST), and bilirubin levels were estimated using specific kits (Fortress diagnostic, Antrim, UK), while total protein and creatinine levels were determined according to the procedure described by Bilanda et al.[21] Total cholesterol, superoxide dismutase (SOD), catalase, malondialdehyde (MDA), and nitric oxide were quantified as previously described,[22-25] while the determination of reduced glutathione (GSH) was performed using a method described by Kouemou et al.[26]

Statistics analysis

Data were provided as microphotography or mean ± standard error of the mean and difference between groups were assessed by one-way analysis of variance followed by Dunnett’s test using Graph Pad Instat Software (version 5.03). P < 0.05 was regarded as statistically significant.

RESULTS

Effect of A. gabonensis extract on body weight gain

Results showed the normal weight growth of the rats of control group [Figure 1a]. Rats treated with CCl4 significantly lost weight every week in comparison with control group. A reduction of 87.50% was recorded in week 9th. A. gabonensis at the dose of 200 mg/kg administered in PREV manner significantly prevent the weight loss of rats compared to CCl4 group and when given in the curative way, A. gabonensis (100 or 200 mg/kg) and SIM (25 mg/kg) significantly improved the weight growth from week 11th when compared to CCl4 group.

Figure 1:
(a and b) Effect of Allanblackia gabonensis aqueous extract on body weight gain and relative organ weight of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. *P < 0.05, **P < 0.01 compared to the control group, ##p<0.01 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis extract on relative organ weight

The relative liver weight of CCl4 group was significantly higher (21.81%) compared to the control group. SIM (25 m/kg) and A. gabonensis (100 or 200 mg/kg) administered preventively or curatively prevented significant increase in liver weight compared to CCl4 group. No significant changes were found in the kidney and heart compared to the control rats [Figure 1b].

Effect of A. gabonensis on hematological parameters

The number of platelets was significantly decreased in CCl4 group compared to control. A. gabonensis (100 or 200 mg/kg) administered preventively or curatively improved the number of platelets [Figure 2a]. No significant modification of white blood cells, red blood cells, and hematocrits was noted compared to the control.

Figure 2:
(a and b) Effect of Allanblackia gabonensis aqueous extract on hematological parameters and total proteins of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. *P < 0.05, **P < 0.01 compared to the control group. # p < 0.05 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis on total protein levels

Total protein levels were significantly decreased (29.80%) in the serum of CCl4 group compared to control group. PREV treatment of rats with A. gabonensis extract (200 mg/kg) or curative administration of A. gabonensis extract (100 or 200 mg/kg) or SIM (25 mg/kg) caused significant increase (P < 0.05) in the serum total proteins level in comparison with CCl4 group. No significant difference was observed in liver and kidney as compared to the control and CCl4 groups. PREV treatment of rats with A. gabonensis extract (200 mg/kg) induced a significant increase in the total protein level in the rat’s heart compared to CCl4 group [Figure 2b].

Effect of A. gabonensis on transaminase activity

A significant increase in ALT activity (125.98%) in the serum of the CCl4 group was recorded compared to control. A. gabonensis extract (200 mg/kg) prevented a significant increase in ALT activity and when given in the curative way, A. gabonensis extract (100 or 200 mg/kg) and SIM significantly reduced serum ALT activity when compared to CCl4 group. No significant modification of ALT activity was observed in the liver and heart as compared to the control group [Figure 3a].

Figure 3:
(a and b) Effect of Allanblackia gabonensis aqueous extract on transaminase levels of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. *P < 0.05, **P < 0.01 compared to the control group, #P < 0.05, ##P < 0.01 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

No significant modifications were found in AST activity in serum, liver and in heart compared to control group. However, rats treated with SIM presented a significant decrease (28.13%) of AST activity in the heart as compared to CCl4 group [Figure 3b].

Effect of A. gabonensis aqueous extract on bilirubin level

Results showed a significant increase of bilirubin level in the liver of CCl4 group compared to the control group. Treatment with SIM and A. gabonensis extract (100 or 200 mg/kg) hindered the significant elevation of bilirubin in the liver [Figure 4a].

Figure 4:
(a and b) Effect of Allanblackia gabonensis aqueous extract on bilirubin and creatinine levels of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. **P < 0.01 compared to the control group. ##P < 0.01 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis extract on creatinine level

In the kidney, creatinine level was found to be significantly increased in the CCl4 group compared to the control. PREV and curative administration of A. gabonensis extract or SIM to rats significantly prevented increase in the renal creatinine level as compared to CCl4 group [Figure 4b]. No significant variations were found in the serum following treatment.

Effect of A. gabonensis extract on SOD activities

Injection of CCl4 caused a significant decrease of SOD activities in the liver (59.77%), kidney (71.63%), and heart (57.67%) as compared to control [Figure 5a]. PREV administration of A. gabonensis extract (200 mg/kg) to rats significantly prevented the decrease of the SOD activity in the liver, kidney, and heart as compared to CCl4 group. Administration of SIM or A. gabonensis extracts (100 or 200 mg/kg) after induction of liver injury triggered significant elevation of SOD activity in all tissues as compared to CCl4 group.

Figure 5:
(a and b) Effect of Allanblackia gabonensis aqueous extract on superoxydismutase and glutathione activities of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. *P < 0.05, **P < 0.01 compared to the control group, #P < 0.05, ##P < 0.01 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis extract on GSH level

Injection of CCl4 caused a significant decrease in GSH level in the liver (62.54%) and kidney (54.33%) compared to control. Results showed significant increases in GSH level in the liver of the rats treated both preventively and curatively with the plant aqueous extract and SIM as compared to CCl4 group [Figure 5b]. A significant increase in the heart GSH level was observed in the PREV group compared to CCl4 group.

Effect of A. gabonensis on catalase activity

CCl4 administration caused a significant decrease (26.67%) of catalase activity in CCl4 group compared to control group. Treatment with A. gabonensis or SIM significantly improved the catalase activity as compared to CCl4 [Figure 6a].

Figure 6:
(a and b) Effect of Allanblackia gabonensis aqueous extract on catalase activity of rat treated with carbon tetrachloride (CCl4) Each bar represents mean ± SEM, n = 5. *P < 0.05, **P < 0.01 compared to the control group, #P < 0.05, ##P < 0.01 compared to CCl4 group. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis extract on MDA level

MDA levels were significantly increased in the liver (59.43%), kidney (28.75%), and heart (33.65%) after administration of CCl4, compared to control. Treatment with A. gabonensis at 200 mg/kg in PREV study, and A. gabonensis (100 or 200 mg/kg) and SIM (25 mg/kg) in curative study significantly decreased MDA levels in the liver when compared to CCl4 group [Figure 6b].

Effect of A. gabonensis extract on nitrite oxide level

The administration of CCl4 caused a non-significant increase of nitrite oxide in the liver (27.32%), kidney (20.36%), and heart (3.51%) in comparison to the control. A. gabonensis or SIM did not induce any significant changes in nitrite oxide levels in the liver, kidney, and heart when compared to control and CCl4 groups [Figure 7].

Figure 7:
Effect of Allanblackia gabonensis aqueous extract on nitrite oxide levels of rat treated with carbon tetrachloride (CCl4). Each bar represents mean ± SEM, n = 5. PREV: Preventive group (E 200 mg/kg + CCl4). SIM: Silymarin at the dose of 25 mg/kg. E 100 or 200: Extract of trunk bark of A. gabonensis at the dose of 100 or 200 mg/kg.

Effect of A. gabonensis aqueous extract on kidney histological structure

The kidney shows a normal appearance of structures such as the glomerulus, Bowman’s capsule, urinary space, and renal tubules in the control group [Figure 8a]. The kidney of the CCl4 rats shows tubular clarification, the urinary space is somewhat large, but most importantly, there is extensive necrosis of the renal tubules [Figure 8b]. In the PREV group, tubular clarification was observed, and the other structures are normal [Figure 8c]. Rats treated with SIM show slight tubular clearing and a very large urine space [Figure 8d]. The renal section of rats treated curatively with the plant extract shows normal architecture except for the tubular clarification observed especially at the lowest dose [Figure 8e and f].

Figure 8:
Microphotography of kidney of rats treated with carbon tetrachloride (CCl4) and Allanblackia gabonensis renal histological sections stained with hematoxylin eosin (×400), (a) kidney section of control rat, (b) kidney section of CCl4 rat, (c) kidney section of preventive rat (E 200 mg/ kg + CCl4), (d) kidney section of CCl4+Silymarin 25mg/kg, (e) kidney section of CCl4 + E 100 mg/kg, and (f) kidney section of CCl4 + E 200 mg/kg. G: Glomerulus, Bc: Bowman’s capsule, Rt: Renal tubule, U: Urinary space, Tn: Tubular necrosis, Tc: Tubular clarification.

Effect of A. gabonensis aqueous extract on liver histological structure

The livers of the control rats showed a normal appearance with hepatocytes cells well-organized around the portal space [Figure 9a]. However, microphotography of the livers of the CCl4 group of rats showed steatosis and necrosis of the hepatocytes [Figure 9b]. A PREV treatment with aqueous extract of A. gabonensis prevented the installation of the deteriorations observed in the CCl4 treated group [Figure 9c]. The livers of rats treated with SIM showed a significant reduction in lesions as compared to the control [Figure 9d]. The livers of rats treated with plant extract at 100 or 200 mg/kg showed mild steatosis and necrosis of hepatocytes [Figure 9e and f].

Figure 9:
Microphotography of liver of rat treated with carbon tetrachloride (CCl4) and Allanblackia gabonensis histological sections stained with hematoxylin eosin (×400). (a) Liver section of control rat, (b) liver section of CCl4 rat, (c) liver section of preventive rat (E 200 mg/kg + CCl4), and (d) liver section of CCl4 +Sily25. (e) Liver section of CCl4 + E 100 mg/kg and (f) liver section of CCl4 + E 200 mg/kg. H: Hepatocyte, St: Steatosis, Ps: Portal space, Hn: Hepatocyte necrosis.

DISCUSSION

Hepatoprotective activity of A. gabonensis was done on CCl4-induced rat chronic liver damage since it has been demonstrated to possess antioxidant, anti-inflammatory properties, and protective effects against acute acetaminophen-induced liver and kidney disorders in rats.[8] This work has shown that the aqueous extract of A. gabonensis trunk bark may protect the liver against chronic damage caused by CCl4 by improving the weight growth of rats, the biomarkers of the liver and kidney functions and by reducing oxidative stress induced by prolonged treatment with CCl4.

Our results showed a significant decrease in the body mass of the CCl4-treated rats compared to control group. Change in body weight is an adequate index to evaluate the seriousness of pathologies and to appreciate the normal functioning of the body. Thus, a loss of body mass is indicative of a state of dysfunction within an organism.[20] Rats treated with A. gabonensis extract showed a markedly improved weight growth of rats compared to CCl4 group, suggesting beneficial effect of the extract against CCl4-induced chronic liver injury. It has been reported that many plants have the ability to protect against liver injury.[27] The aptitude of plant component to inhibit the aromatized activity of cytochrome P-450 by favoring liver regeneration is another and interesting factor in the hepatoprotective effect.[28]

It is important to find compounds that can prevent liver damage from free radicals generated by toxic chemicals.[29] Many compounds known to be beneficial against CCl4-mediated liver injury exert their protective action through toxin-mediated lipid peroxidation either through a decreased production of CCl4-derived free radicals or by the antioxidant activity of the protective agents themselves.[30,31] Recently, interest has increased considerably in finding naturally occurring antioxidants for use in food due to their potential in health promotion and disease prevention, and their high safety and consumer acceptability.[32] In search of novel sources of antioxidants in the past years, medicinal plants have been extensively studied for their antioxidant activity.[33]

Liver function tests such as ALT, AST, and total proteins can be used to assess liver status. Transaminase is a cytosolic enzyme that contributes to metabolic activity of the liver. The elevated plasma activity of this enzyme indicates hepatocyte damage.[34] Our results displayed a significantly increased level of ALT in CCl4 group when compared to the control group and this corroborate studies that demonstrated an increase in plasma levels of ALT due to CCl4 injection to rat.[35] Administration of A. gabonensis aqueous extract has prevented significant elevation of ALT activity in PREV study and decrease considerably the level of ALT in curative study compared to CCl4 control. An adequate serum protein level indicates normal physiological activity of hepatocytes.[34] Rats treated with A. gabonensis aqueous extract showed a total serum protein level comparable to that of the control, regardless of treatment. These results showed that extract may have a hepatoprotective activity against liver damage due to chronic administration of CCl4.

Chronic administration of CCl4 has caused a significant decrease of platelets. Blood coagulation requires that platelets be in sufficient size, number, and function in the absence of which a satisfactory plug may not occur, and bleeding may continue as a result of a breach in the vascular endothelium.[36] A. gabonensis extract has elevated the level of platelets compared to control group. Similar results were obtained by Keon et al.[37]

The metabolism of toxic chemicals generates free radicals that cause liver damage.[29] Many compounds that have a beneficial effect against CCl4-induced liver damage exert their protective action on CCl4-induced lipid peroxidation, either by causing a decrease in the production of CCl4-derived free radicals, or by exerting direct antioxidant activity (scavenging activity) or indirectly through activation of the endogenous antioxidant system.[30,31] The results of this study showed that CCl4 intoxication of study rats, resulted in a significant reduction of reduced GSH level, and decreased in SOD and catalase activity compared to the control. Treatment with A. gabonensis extract has prevented a significant decrease in reduced GSH level and in SOD and catalase activity compared to control group in both PREV and curative studies. These results suggest that A. gabonensis extract would provide the tissue with better protection against oxidative stress by contributing to the neutralization of free radicals. The PREV and curative administration of A. gabonensis extract to the rats maintained MDA levels in the liver tissue similar to that of the control rats and would confirm the protective properties of the plant extract against CCl4-induced liver damage in rat.

Histopathological analysis of liver sections from CCl4 rats provides support for the previous biochemical analyses. Observation of the liver sections showed hepatic lesions, such as hepatocyte steatosis and necrosis. PREV or curative administration of the aqueous extract of A. gabonensis remarkably reduced these hepatic lesions, thus preserving the appearance of the liver parenchyma. In the kidneys, the extract also reduced necrosis of the renal tubules. This hepato- and nephroprotective activity of the aqueous extract may be due to the antioxidant properties of this plant. The previous phytochemical study of the stem bark of A. gabonensis resulted in the identification, isolation and characterization of xanthone derivatives, one polyisoprenylated benzophenone, guttiferone F, one flavanol, epicathechin, two phytosterols, β-sitosterol, and campesterol.[14,38] The antioxidant effectiveness in natural substances was reported to be mostly due to the presence of phenol compounds.[39-42] Moreover, strong relationship between the phenols and antioxidant activity was shown by Velioglu et al.,[43] Kahkonen et al.,[44] and Javanmardi et al.[45] A. gabonensis showed its ability to preserve and restore the normal functional status of liver under the toxic effects of CCl4.

CONCLUSION

The results of our study show that the aqueous extract of A. gabonensis trunk bark has PREV and curative effects against CCl4-induced chronic liver injury in rats. This extract reduced the hepatoxicity induced by CCl4 administration as shown by the rats’ body weight increase and the liver markers. These protective effects may be related to the antioxidant properties of the aqueous extract of the plant. These results show evidence for a better exploitation of this plant, whose antioxidant properties have been demonstrated and which could be useful for a drug formulation against liver diseases.

Acknowledgment

We thank the Faculty of Sciences of the University of Yaoundé I the University of Ngaoundéré and the University of Douala for the support with their working facilities.

Disclaimer

Dr Chiogo Vouffo contributed to this publication in her personal capacity. The views expressed in this publication are her own and do not necessarily reflect the official policy of the U.S. Food and Drug Administration.

Declaration of patient consent

Patient’s consent not required as there are no patients in this study.

Conflicts of interest

There are no conflicts of interest as far as this work is concerned.

Financial support and sponsorship

None.

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