Background: Antioxidant and antityrosinase activities of medicinal plants, together with their various health benefits have received attention in recent times. However, with wide ethnobotanical uses of Phyllanthus amarus, data on in-vitro skin depigmentation activity and cytotoxicity, as well as its impact on mediators of reactive oxygen species (ROS) are still lacking. This present study is, therefore, designed to evaluate its tyrosinase inhibitory action, antioxidant potentials and cytotoxic activities.
Methods: In this study, quantitative determinations of polyphenols, flavanol, flavonol, flavonoids, oxygen reducing antioxidant capacity (ORAC), Trolox equivalent antioxidant capacity (TEAC) were done. Also, the tyrosinase inhibitory efficacy of the hexane, methanolic and aqueous extracts of Phyllanthus amarus were evaluated using ELISA-based methods. Cytotoxicity studies were done with mouse Sertoli (TM4) cells, using MTT assay and cell counts.
Results: The hexane and aqueous extracts exhibit significant antityrosinase activity (p<0.05) (IC50= 116.08 and 129.25 μg/mL respectively) while its methanolic extract produces no statistically significant finding. Higher total polyphenol, flavonoids and flavonol were seen in the methanolic fraction of the extract. Besides, higher radical cation scavenging (TEAC) activity was observed in the aqueous extract. These values were statistically significant (p<0.0001), whereas ORAC results on the methanolic extract show significantly (p<0.0001) higher oxygen reducing antioxidant potential than the aqueous extract. The aqueous extract showed the highest mitochondrial dehydrogenase activity at lower concentrations (0.01 to 10 µg/ml). Here, TM4 cell numbers were also significantly higher compared to the untreated control. Sertoli cell viability was compromised after exposure to higher extract concentrations (100 to 1000 µg/ml).
Conclusion: The hexane and aqueous extracts of Phyllanthus amarus possess good tyrosinase inhibitory action when compared to the reference kojic acid. Also, it demonstrated high antioxidant potentials by its ability to scavenge oxygen radicals reduce ferric ion and inhibit ABTS radical. Lower extract concentrations stimulate Sertoli cell proliferation, which might be due to phytoestrogenic activities of Phyllanthus amarus.