Bitter kola extract increases longevity, neutralises toxic effect of pesticides

* Nigerian researchers identify Kolaviron as therapeutic candidate for insecticide-induced Parkinson ‘s disease

For the first time, scientists have demonstrated that regular intake of bitter kola (Garcinia kola) increases life span and life expectancy as well as neutralize the effects of toxic substances.

The study published in the journal Pesticide Biochemistry and Physiology is titled “Garcinia kola seed biflavonoid fraction (Kolaviron), which increases longevity and attenuates rotenone-induced toxicity in Drosophila melanogaster.”

The researchers from the College of Medicine, University of Ibadan, and University College Hospital, Ibadan, Oyo State, concluded: “Kolaviron extends the lifespan of Drosophila, and protects against rotenone-induced toxicity by preventing oxidative stress and inflammation in D. melanogaster. This protective influence of Kolaviron was partly associated with its free radical scavenging and antioxidant properties. Thus, Kolaviron can be a therapeutic candidate for a rotenone-induced model of Parkinson’s Disease (PD).”

Parkinson’s disease is a long-term, degenerative, neurological disease that causes a person to lose control over some body functions. Symptoms start gradually, sometimes starting with a barely noticeable tremor in just one hand. Tremors are common, but the disorder also commonly causes stiffness or slowing of movement.

Drosophila melanogaster (fruit fly) is a small, common fly found near unripe and rotted fruit. It has been in use for over a century to study genetics and behaviour.

Rotenone, a naturally occurring and commonly used pesticide, has been established as a model for inducing PD in rodents.

Kolaviron is a biflavonoid complex from Garcinia kola seeds with antioxidative and anti-inflammatory properties.

The researchers evaluated the ameliorative role of Kolaviron on rotenone-induced toxicity in Drosophila melanogaster. Flies for longevity study were exposed to Kolaviron (100–500 mg/kg diet) throughout the lifespan. For the biochemical study, Groups A, B, and C flies were treated with ethanol (2.0 per cent, control, vehicle), Kolaviron (200 mg/kg diet) and rotenone (250 μM) respectively. Flies in Group D were co-treated with both rotenone (250 μM) and Kolaviron (200 mg/kg diet) for seven days. Subsequently, selected markers of antioxidant status, inflammatory and neurotoxicity were evaluated in the flies.

The results from longevity experiment showed that Kolaviron (200, 100, 300 and 400 mg/kg) extended the lifespan of flies by 38.2 per cent, 20.6 per cent, 11.8 per cent and 2.9 per cent respectively. Also, Kolaviron attenuated rotenone-induced inhibition of catalase, glutathione-S- transferase and acetylcholinesterase activities and depletion of total thiols content in flies.

The researchers demonstrated how Kolaviron prevented rotenone-induced increases in hydrogen peroxide and nitric oxide (nitrite and nitrate) levels and improved rotenone-induced decrease in locomotor performance of flies. “Overall, this study evidenced for the first time, the lifespan extension property of Kolaviron and its chemoprotective role on rotenone-induced toxicity in D. melanogaster via anti-oxidative and anti-inflammatory mechanisms,” they noted.

Intriguingly, D. melanogaster is being used as a suitable model to investigate the therapeutic/preventive roles of plants- derived products on chemical-induced toxicity.

Kolaviron (KV) is a golden-yellow defatted ethanol fraction of Garcinia kola seeds. Its major components include Garcinia biflavonoids GB1, GB2, and kolaflavanone. Several studies in our laboratory have been reported on the protective role of Kolaviron against chemical-induced oxidative stress. Also, Kolaviron inhibited hydroxyl and superoxide anion radicals, which have been implicated in lipid peroxidation. In these contexts, the protective mechanisms of Kolaviron have been linked with its ability to scavenge free radicals and reactive electrophilic metabolites and induce gene expressions and activities of xenobiotic metabolizing enzymes.

Based on the reported antioxidant property of Kolaviron, the present study sought to investigate for the first time, its role in the lifespan and its ameliorative potential on rotenone-induced model of PD in D. melanogaster.

Specifically, the researchers evaluated selected markers of oxidative stress and antioxidants (hydrogen peroxide level, catalase, and glutathione-S-transferase activities), inflammation (nitric oxide level), neurotoxicity (negative geotaxis and acetylcholinesterase activity) and fly emergence in D. melanogaster dosed with rotenone and Kolaviron.

The researchers further explained: “In recent times, D. melanogaster is extensively being employed to obtain mechanistic data on the pathophysiology of several diseases induced by pesticides and environmental toxins. It is also a useful platform for the screening of various reputed phytochemicals with potent anti-oxidative and anti-inflammatory properties. Here, we sought to evaluate the ameliorative role of Kolaviron on rotenone-induced toxicity in D. melanogaster. This study provides evidence for the first time that Kolaviron indeed extended the lifespan and ameliorated rotenone-induced behavioural deficits, oxidative stress and inflammation in D. melanogaster.

“Studies have shown that consumption of diets fortified with supplements rich in antioxidant property contributes to lifespan extension in organisms. In this context, the lifespan extension role of Kolaviron (200 mg/kg) might be due to its anti-oxidant property. The 200 mg/kg of Kolaviron was the best concentration that extended the lifespan of flies in comparison with the other doses of KV (100, 300 and 400 mg/kg). This implies that doses higher than 400 mg/kg such as 500 mg/kg might reduce survival with respect to the control. Additionally, the fact that the average number of days corresponding to the period when 50 per cent of mortality occurred were 15, 22, 32, 25, 18 and 20 days for control, and flies treated with Kolaviron (100, 200, 300, 400 and 500mg/kg) respectively, implies that KV increased the number of days required for 50 per cent mortality to occur when compared with the control flies.

“The results revealed that flies treated with rotenone exhibited locomotor deficit, via the impairment of negative geotaxis (climbing), which is one of the features of PD. It is interesting to note, however, that Kolaviron ameliorated the movement disturbance induced by rotenone. Apart from this, Kolaviron also prevented rotenone-induced inhibition of acetylcholinesterase activity in the flies. This enzyme hydrolyses acetylcholine, a neurotransmitter that plays a vital role in the regulation of motor function and locomotion. Thus, the observed decrease in AChE activity in the present study might hamper normal neurotransmission in the flies.

“Since oxidative stress has been implicated in the pathogenesis of PD, we evaluated selected markers of oxidative stress and antioxidant status in D. melanogaster. We found that rotenone increased hydrogen peroxide generation in the flies inhibited catalase and GST activities and depleted total thiols level in D. melanogaster. The observation that rotenone increased hydrogen peroxide level is consistent with the previous study by Zhou et al., who reported that rotenone-dependent elevation of hydrogen peroxide inhibited mTOR-mediated phosphorylation of S6K1 and 4E-BP1 which resulted in toxicity to neuronal cells. Indeed, hydrogen peroxide-mediated injuries to Deoxyribonucleic Acid (DNA)/genetic material, proteins and lipid components of tissues have been linked with several diseases in living organisms.

“The role of catalase in living systems is to catalyze the dismutation of hydrogen peroxide to water and molecular oxygen, thereby minimizing the risks associated with hydroxyl radical generation via the Fenton reaction. Thus, the observed inhibitory effect of rotenone on catalase activity in D. melanogaster, suggests an increased susceptibility of flies to oxidative stress. This finding was similar to the study by Javed et al., where rotenone inhibited catalase activity in rats. Interestingly, the increased H2O2 generation and diminution in catalase activity by rotenone were prevented in flies co-treated with Kolaviron and rotenone, thus, confirming its anti-oxidative property.

“In addition, glutathione-S-transferases (GSTs) belong to the phase II family of detoxifying enzymes. They catalyze the conjugation of GSH to the electrophilic centers of exogenous and endogenous electrophiles. Apart from this, GSTs also play vital roles in the regulation of processes involved in the survival of organisms to oxidative stress. Thus, the observed rotenone-induced inhibition of GST activity implies that the response of the flies to combat oxidative stress was further compromised. However, the inhibitory role of rotenone on GST activity was prevented in flies concurrently exposed to rotenone and Kolaviron.

“Indeed, Kolaviron has been reported to prevent toxicant-induced depletion of GST activity. Moreover, rotenone depleted the total thiols level in D. melanogaster. Total thiols comprise of GSH and several other thiol-containing compounds in tissues. The determination of thiols is vital because of the vital roles they play in several biological processes. For instance, GSH is an important antioxidant in living organisms that prevents damage to cellular components caused by ROS, free radicals, and peroxides. Thus, total thiols depletion by rotenone showed that the flies’ ability to combat free radical damage would be hampered. However, the observation that Kolaviron ameliorated rotenone-induced depletion of total thiols further confirms its anti-oxidative potency. It is pertinent to note that depletion of cytosolic GSH in the substantia nigra of dopaminergic neurons is one of the vital events, which occurs, in human PD subjects. Thus, Kolaviron may represent an important therapeutic candidate to lessen the burden of PD. Indeed, several plant-based products have been reported to lessen the toxic impacts of toxic agents, and thus can be used by humans as therapeutic agents against neurodegenerative and other diseases in which oxidative stress is implicated.

“In the present study, rotenone exposure significantly increased nitric oxide (nitrite and nitrate) level in D. melanogaster. Indeed, nitric oxide (NO) is a highly diffusible and short-lived free radical gas. It rapidly recombines to form the stable metabolites nitrate and nitrite. Thus, nitrate (NO3−) and nitrite (NO2−) anions are regarded as stable products of NO oxidation. Also, the nitrate—nitrite—nitric oxide reductive pathway is used as an alternative pathway to the enzymatic formation of NO via the oxidation of L-arginine with molecular oxygen. Our observation is similar to the report of Zhang et al., in which NO level was elevated in rats dosed with rotenone.

“Nitricoxide is a vital molecule in living organisms because it participates in a number of pathological and physiological processes. Nitric oxide is considered a pro-inflammatory mediator when there is overproduction by the inducible nitric oxide synthase (iNOS). Thus, the apparent suppression of rotenone-mediated accumulation of NO by Kolaviron suggests its anti-inflammatory property.

“Lastly, it is too early to speculate the reasons for the inability of Kolaviron (200 mg/kg) to restore flies` emergence to the threshold of the control, in the group co-treated with rotenone. Nevertheless, the fact that the emergence in the group treated with Kolaviron alone was slightly higher than that of the control, and the fact that the group co-treated with Kolaviron and rotenone had slight emergence, while rotenone group had none, further suggests its beneficial role in the flies.”