E. Olatunde Farombi

African indigenous plants with chemotherapeutic potentials and biotechnological approach to the production of bioactive prophylactic agents

Undoubtedly medicinal plants are relevant in both developing and developed nations of the world as sources of drugs or herbal extracts for various chemotherapeutic purposes. Also the use of plantderived natural compounds as part of herbal preparations as alternative sources of medicaments continues to play major roles in the general wellness of people all over the world. The African continent contains some of the richest biodiversity in the world, and abounds in plants of economic importance and plants of medicinal importance which when developed would reduce our expenditure on imported drugs to meet our health needs. Herbal-based and plant-derived products can be exploited with sustainable comparative and competitive advantage. This review presents some indigenous African plants with chemotherapeutic properties and possible ways of developing them into potent pharmacological agents using biotechnological approaches.

Antioxidant and Scavenging Activities of Flavonoid Extract (Kolaviron) of Garcinia kola Seeds

The antioxidant and scavenging properties of kolaviron, a flavonoid extract of Garcinia kola seeds, were evaluated in a series of in vitro assays involving free radicals and reactive oxygen species. Kolaviron exhibited markedly reducing power and antioxidant activity by inhibiting the peroxidation of linoleic acid. Kolaviron exhibited 57% scavenging effect on superoxide at a concentration of 1 mg/ml and 85% scavenging effect on hydrogen peroxide at a concentration of 1.5 mg/ml. Similarly, kolaviron, at a concentration of 2 mg/ml, elicited an 89% scavenging effect on a,a-diphenyl-ß-picrylhydrazyl radical, indicating that the extract has effective activities as a hydrogen donor and as a primary antioxidant to react with lipid radicals. Kolaviron reacted with hydroxyl radical (·OH) by inhibiting deoxyribose oxidation induced by a Fenton-type reaction system (Fe 3+ + EDTA/H 2 O 2 /ascorbic acid). The second-order rate constant for the reaction with ·OH was approximately 1.1 × 10 10 M -1 sec -1. Kolaviron was effective at preventing microsomal lipid peroxidation induced by iron/ascorbate in a concentration dependent manner. The overall antioxidant activity of kolaviron on lipid peroxidation might be attributed to its properties of scavenging free radicals and active oxygen species and may relate directly to prevention of propagation of in vivo lipid peroxidation.

Ex-vivo and in vitro protective effects of kolaviron against oxygen-derived radical-induced DNA damage and oxidative stress in human lymphocytes and rat liver cells.

The present study reports the protective effects of kolaviron, a Garcinia biflavonoid from the seeds of Garcinia kola widely consumed in some West African countries against oxidative damage to molecular targets ex-vivo and in vitro. Treatment with hydrogen peroxide (H2O2) at a concentration of 100 μmol/L increased the levels of DNA strand breaks and oxidized purine (formamidopyrimidine glycosylase (FPG) and pyrimidine (endonuclease III (ENDO III) sites) bases in both human lymphocytes and rat liver cells using alkaline single cell gel electrophoresis (the comet assay). Kolaviron was protective at concentrations between 30–90 μmol/L and decreased H2O2-induced DNA strand breaks and oxidized bases. Neither α-tocopherol nor curcumin decreased H2O2-induced DNA damage in this assay. In lymphocytes incubated with Fe3+/GSH, Fe3+ was reduced to Fe2+ by GSH initiating a free radical generating reaction which induced 11.7, 6.3, and 4.9 fold increase respectively in strand breaks, ENDO III and FPG sensitive sites compared with control levels. Deferoxamine (2 mmol/L), an established iron chelator significantly inhibited GSH/Fe3+-induced strand breaks and oxidized base damage. Similarly, kolaviron at 30 and 90 μmol/L significantly attenuated GSH/Fe3+-induced strand breaks as well as base oxidation.Kolaviron (100 mg/kg bw) administered to rats for one week protected rat liver cells against H2O2-induced formation of strand breaks, ENDO III, and FPG sensitive sites, Fe3+/EDTA/ascorbate-induced malondialdehyde formation and protein oxidation using γ-glutamyl semialdehyde (GGS) and 2-amino-adipic semialdehyde (AAS) as biomarkers of oxidative damage to proteins. We suggest that kolaviron exhibits protective effects against oxidative damage to molecular targets via scavenging of free radicals and iron binding. Kolaviron may therefore be relevant in the chemoprevention of oxidant-induced genotoxicity and possibly human carcinogenesis.

Effect of three structurally related antimalarial drugs on liver microsomal components and lipid peroxidation in rats

Changes in microsomal drug oxidizing enzymes, microsomal lipids, hepatic glutathione (GSH), glutathione S-trans-ferase (GST) and malondialdehyde (MDA) formation following administration of rats with therapeutic doses of three structurally related antimalarial drugs, amodiaquine (AQ), mefloquine (MQ) and halofantrine (HF) were investigated. There was a significant decrease in the activities of aniline hydroxylase, p-nitroanisole O-demethylase and pentoxyresorufin O-dealkylase in AQ, MQ and HF treated rats. AQ elicited the greatest effect with 50, 37 and 67% reductions in the activities of aniline hydroxylase, p-nitroanisole O-demethylase and pentoxyresorufin O-dealkylase, respectively. All the drugs prolonged hexobarbital-sleeping time to varying extents. The three drugs increased significantly the cholesterol per phospholipid ratio. AQ, MQ and HF decreased significantly the GSH level, GST activity and increased the formation of MDA. The results indicate that the alterations in hepatic microsomal components and lipid peroxidation caused by the antimalarials are related to the structural differences in the compounds.

Influence of Chloroquine Treatment and Plasmodium falciparum Malaria Infection on Some Enzymatic and Non-enzymatic Antioxidant Defense Indices in Humans

Abstract Background. It is known that malaria infection is accompanied by increased production of reactive oxygen species (ROS) and that malaria parasites are sensitive to oxidative damage. This has been proved by the efficacy of some antimalarial drugs that are known to act via generation of ROS when administered clinically or experimentally. Objective. There is lack of information on the effect of chloroquine on the antioxidant defense systems of normal and malaria infected humans. Since chloroquine has remained the mainstay of therapeutic regimen in malaria endemic zones, the present investigation was therefore undertaken to study the status of blood antioxidant defense mechanism, and oxidative stress following chloroquine treatment in normal and plasmodium infected humans. Methods. Ten healthy persons (5 males and 5 females) with the same age range (18–35 years) were taken as control group. Ten other individuals were treated with 25 mg/kg body with chloroquine over three days. Ten patients with malaria, not under antimalarial therapy were taken as another group, while another set of 10 patients with malaria were treated with 25 mg/kg body weight over three days. Results. The activity of superoxide dismutase was increased by 23% in individuals treated with chloroquine compared to controls while the activity of the enzyme decreased by 26% in malaria patients and by 43% in malaria patients treated with chloroquine. In all the treatment groups, the activities of catalase and glutathione peroxidase were lowered (P<0.001). Similarly the levels of vitamins A, C, and β-carotene were decreased in the treatment groups while plasma ceruloplasmin was increased in the groups. Glutathione and cholesterol levels were decreased while malondialdehyde level was increased significantly. Conclusion. Chloroquine treatment mediated oxidative stress in the host and this effect was exacerbated in Plasmodium falciparum infected patients administered with the drug.

Dried fruit extract from Xylopia aethiopica (Annonaceae) protects Wistar albino rats from adverse effects of whole body radiation.

The effect of dried fruit extract from Xylopia aethiopica (Annonaceae) (XA) and vitamin C (VC) against γ-radiation-induced liver and kidney damage was studied in male Wistar rats. XA and VC were given orally at a dose of 250 mg/kg, orally for 6 weeks prior to and 8 weeks after radiation (5 Gy). The rats were sacrificed after 1 and 8 weeks of single exposure to radiation. Results showed that all animals in un-irradiated group survived (100%), while 83.3% and 66.7% survived in XA- and VC-treated groups, respectively, and 50% survived in irradiated group. The levels of serum, liver and kidney lipid peroxidation (LPO) were elevated by 88%, 102% and 73% after 1 week of exposure, and by 152%, 221% and 178%, after 8 weeks of exposure, respectively. Treatment with XA and VC significantly (p<0.05) decreased the levels of LPO in the irradiated animals. Also, γ-radiation caused significant decreases (p<0.05) in the levels of liver glutathione (GSH), glutathione-S-transferase (GST), catalase (CAT), superoxide dismutase (SOD), kidney GSH and SOD by 41%, 60%, 81%, 79%, 72% and 58% after 1 week of exposure. Similarly, γ-radiation caused significant increases (p<0.05) in the levels of serum alanine (ALT) and aspartate aminotransferases (AST) after 8 weeks of exposure. Precisely, ALT and AST levels were increased by 69% and 82%, respectively. These changes were significantly (p<0.05) attenuated in irradiated animals treated with XA and VC. These results suggest that XA and VC could increase the antioxidant defence systems in the liver and kidney of irradiated animals, and may protect from adverse effects of whole body radiation.

Hepatic drug metabolizing enzyme induction and serum triacylglycerol elevation in rats treated with chlordiazepoxide, griseofulvin, rifampicin and phenytoin

Five days intraperitoneal administration of rats with chlordiazepoxide (0.4 mg/kg), griseofulvin (7 mg/kg), rifampicin (8. 6 mg/kg), phenytoin (4.3 mg/kg) and phenobarbitone (1.4 mg/kg; an established inducer of microsomal enzymes) caused a significant increase in serum triacylglycerol (P<0.001) and the activities of aniline hydroxylase, aminopyrine N-demethylase and p-nitroanisole O-demethylase (P<0.001). Aniline hydroxylase, aminopyrine N-demethylase and p-nitroanisole O-demethylase activities were increased 1.48-, 1.15- and 1.47-fold, respectively, in chlordiazepoxide-treated rats, 1.65-, 1.20- and 1.38-fold in griseofulvin-treated rats, 1.74-, 1.36- and 1.44-fold in rifampicin-treated rats, 1.56-, 1.29- and 1.62-fold in phenytoin-treated rats and 2.26-, 1.72- and 1.93-fold in phenobarbitone-treated rats. Chlordiazepoxide, griseofulvin, rifampicin, phenytoin and phenobarbitone increased the activity of cytosolic phosphatidate phosphohydrolase by 52, 58, 67, 73 and 82%, respectively, while the drugs elicited 50, 60, 60, 73 and 87% increases in the activity of the microsomal phosphatidate phosphohydrolase. Similarly, chlordiazepoxide, griseofulvin, rifampicin, phenytoin and phenobarbitone elicited 2.4-, 2.39-, 2.34-, 1.69- and 3.75-fold increases in serum triacylglycerol concentrations. The correlations between serum triacylglycerol concentrations and the activities of aniline hydroxylase, aminopyrine N-demethylase and p-nitroanisole O-demethylase were significant in all treatment groups (r=0.83, r=0.92 and r=0.87, respectively, n=30, P<0.001). Our results suggest that induction of hepatic enzymes by the administered drugs may lead to hypertriglyceridaemia as an adverse effect, possibly by inducing the activity of regulatory enzymes in the biosynthesis of triglyceride.

Possible ameliorative effects of kolaviron against reproductive toxicity in sub-lethally whole body gamma-irradiated rats.

Ionizing radiation is one of the environmental factors that may contribute to reproductive dysfunction by a mechanism involving oxidative stress. We investigated the possible ameliorative effects of kolaviron (KV) (a biflavonoid from the seeds of Garcinia kola) on sperm characteristics, testicular lipid peroxidation (LPO) and antioxidant status after a whole body γ-irradiation in Wistar rats. Vitamin C (VC) served as standard antioxidant in this study. The study consists of four groups of 6 rats each. Group I received corn oil, whereas group II received a single dose of γ-radiation (5 Gy). The animals in groups III and IV were pretreated with KV (250 mg/kg) and VC (250 mg/kg) by oral gavage five times in a week, respectively, for 6 weeks prior to and 8 weeks after exposure to γ-radiation. Gamma-irradiation resulted in a significant (p<0.05) decrease in body weight and relative testes weight. Also, γ-irradiation significantly (p<0.05) decreased the activities of superoxide dismutase, catalase and glutathione S-transferase as well as glutathione level, but markedly elevated malondialdehyde levels in the serum and testes. Irradiated rats showed testicular degeneration with concomitant decrease in sperm motility and viability. Although sperm abnormalities significantly increased, it has no effect on the epididymal sperm count. KV and VC significantly (p<0.05) decreased the body weight loss and increased relative testes weights of the rats. Furthermore, supplementation of KV and VC ameliorated radiation-induced toxicity by increasing the activities of antioxidant enzymes, decreased LPO and abrogated testicular degeneration. Taken together, γ-irradiation caused reproductive dysfunction by depleting the antioxidant defence system in the rats, while administration of KV or VC ameliorated the radiation-induced testicular toxicity.

Chloramphenicol and Ampicillin-Induced Changes in Rat Hepatic Esterase and Amidase Activities

The influence of ampicillin and chloramphenicol administered intraperitoneallysingly or in combination on the protein content and the activities of hepaticsterase and amidase have been investigated in rats. The results have beencompared to the effects of phenobarbitone (inducer) andp-nitrophenyl-phosphate (inhibitor) of hepatic hydrolases.Ampicillin pretreatment reduced protein level and amidase activity by3.5% each but caused a significant increase (8.1%) in total esteraseactivity compared to controls. Chloramphenicol treatment caused an overalldecrease in protein level, esterase and amidase activities respectively by11%, 11%, and 35% over controls.Combined administration of both drugs resulted in a decrease in protein,esterase and amidase activities by 11.5%, 12.5%, and 41.2% respectively,thus mimicking the effects obtained with chloramphenicol alone.The changes induced by administration of the drugs particularly incombination on the constituent enzymes of rat hepatic hydrolases may affectthe ability of the body to deal with exposure to environmental chemicals ifextrapolated to man.

Antimalarial Drugs Exacerbate Rat Liver Microsomal Lipid Peroxidation in the Presence of Oxidants

The study was undertaken to evaluate the effect of prior treatment of rats with the antimalarial drugs amodiaquine (AQ) mefloquine (MQ) and halofantrine (HF) on rat liver microsomal lipid peroxidation in the presence of 1 mM FeSO4, 1 mM ascorbate and 0.2 mM H2O2 (oxidants). Ingestion of α-tocopheral, a radical chain-breaking antioxidant was also included to assess the role of antioxidants in the drug treatment. In the presence of oxidants AQ, MQ and HF elicited 288%, 175% and 225% increases in malondialdehyde (MDA) formation while the drugs induced 125%, 63% and 31% increases in the absence of oxidants respectively. Similarly, AQ, MQ and HF induced lipid hydroperoxide formation by 380%, 256%, 360% respectively in the presence of oxidants and 172%, 136% and 92% in the absence of exogenously added oxidants respectively. α-tocopherol reduced AQ, MQ and HF-induced MDA formation by 40%, 55% and 52% respectively and lipid hydroperoxide formation by 53%, 59% and 54% respectively. Similarly, α-tocopherol attenuated the AQ, MQ and HF-induced MDA formation by 49%, 51% and 51% in the presence of oxidants and lipid hydroperoxide formation by 61%, 62% and 47% respectively. The results indicate that rat liver microsomal lipid peroxidation could be enhanced by antimalarial drugs in the presence of reactive oxygen species and this effect could be ameliorated by treatment with antioxidants.