Isolation of leaf and root extracts from Allium sativum and Mentha piperita plants; evaluation of their antioxidant and anti-tyrosinase activities in-vitro

Abstract

Abstract-Tyrosinase is a key enzyme of melanogenesis which determines the mammalian skin, hair and eye colour. Hyper-pigmentation leads to various skin disorders like melasma, sunspots, age spots and freckles. Moreover, abnormal skin pigmentation is a serious aesthetic concern which leads to psychosocial problems. Thus to achieve melanin inhibition, inhibition of tyrosinase might be an effective approach. To this end we prepared methanolic (MeOH) extracts from leaves and roots of Allium sativum (AS) and Mentha piperita (MP), which were further processed for 1:1 fractional distillation to prepare methanolic n-hexane (MeOH_n-Hx), methanolic ethyl acetate (MeOH_EA) and methanolic chloroform (MeOH_CHCl₃) extracts, aiming to evaluate tyrosinase and anti-oxidant activities in-vitro. Our results confirmed that all MeOH-crude AS and MP extracts showed significant anti-oxidant activity with IC₅₀ values ranging from 0.05 ± 0.2 mg/ml to 4.3 ± 2.3mg/ml. Moreover, AS and MP all 16 extracts have significant anti-tyrosinase activity with IC₅₀ range from 0.014 ± 0mg/ml to 1.205 ± 0.07mg/ml. Interestingly, AS leaf MetOH_EA, AS leaf MetOH_CHCl₃, AS root MetOH_EA and MP leaf MetOH_CHCl₃ showed significant anti-tyrosinase activity even higher than positive control kojic acid. AS leaf MetOH_CHCl₃ extract being the most potent among all tested extracts is proposed as potential candidate to treat tyrosinase rooted hyper-pigmentation in future.