Phytochemical constituents and anti-tyrosinase activity of Macadamia integrifolia leaves extract

Abstract

Macadamia integrifolia Maiden & Betche is cultivated around the world for its highly valued nuts (macadamia nuts). Although the chemical composition of the edible macadamia oil has been repeatedly investigated, other plant organs have not been phytochemically or biologically assessed. In this study, ethanolic extract of M. integrifolia leaves was phytochemically investigated which led to the isolation of 6 compounds. Two functional galactolipids, i.e., monogalactosyl diacylglycrol 36:4 (MGDG 36:4), digalactosyl monoacylglycerol 18:2 (DGMG 18:2), gallic acid and protocatechuic acid were identified in the genus Macadamia for the first time, in addition to the cyanogenic glycoside dhurrin and β-sitosterol. Additionally, anti-tyrosinase activity of the extract, its fractions and isolated compounds was investigated and a good tyrosinase inhibitory activity was observed for the extract, IC₅₀=85 µg/mL and its polar fractions (ethyl acetate at 60 µg/mL and n-butanol at 75 µg/mL), with gallic acid showing strong anti-tyrosinase activity at IC₅₀ 56 µg/mL.

Graphical Abstract

Keywords:

• Macadamia integrifolia
• galactolipids
• MGDG 36:4
• DGMG 18:2
• dhurrin
• anti-tyrosinase
• gallic acid

Disclosure statement

No potential conflict of interest was reported by the authors.