Some Antioxidant Properties of Components from The Flower of Ochna integerrima and Their Beneficial Effects on HaCaT Keratinocytes and In Silico Analysis on Tyrosinase

Four compounds, luteolin ( 1 ), 6- γ , γ -Dimethylallylquercetin 7- O - β -ᴅ-glucopyranoside ( 2 ), 6- γ , γ -Dimethylallylkaempferol 7- O - β -ᴅ-gluco-pyranoside ( 3 ), and 6- γ , γ -Dimethylallyldihydrokaempferol 7- O - β -ᴅ-glucoside ( 4 ), were isolated for the first time from EtOAc extract of the O. integerrima   flower. We then evaluated the antioxidant effects of EtOAc, n -butanol, and MeOH extracts and their effects on H 2 O 2 against oxidative stress in HaCaT keratinocyte cell lines. Furthermore, 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH · ) radical scavenging activities of 1 - 4 were determined and their mechanisms of action on tyrosinase were predicted by in silico studies. The results revealed that the EtOAc extract and 1 - 3 exhibited good DPPH˙radical scavenging activity. Furthermore, this extract also had a significant protective effect against H 2 O 2 -induced oxidative stress in HaCaT cells. In silico studies indicated that the activity of 1 - 3 may be due to tyrosinase inhibition with MM-GBSA free binding energies of -78.9, -70.1, -71.1 kcal mol -1 , respectively, compared to 4 with an energy -56.9 kcal mol -1 .