Potential antioxidant, anti-aging enzymes, and anti-tyrosinase properties of Macadamia (Macadamia integrifolia) pericarp waste products

Abstract

Macadamia integrifolia pericarps are waste products from M. integrifolia nut production. This study aimed to investigate the potential use of M. integrifolia pericarp extracts as cosmeceutical active ingredients. The pericarp of M. integrifolia was extracted by sequential maceration using various solvents, starting with n-hexane, followed by ethyl acetate and 95% v/v ethanol. The extracts were then investigated for their antioxidant activities using 2,2’-diphenyl-1-picrylhydrazyl (DPPH), 2'-azinobis (3-ethylbenzothiazoline-6-sulfonic acid), and ferric reducing/ antioxidant power assay. The whitening effects of the extracts were determined through tyrosinase inhibition when the substrates were L-tyrosine and L-3,4-dihydroxyphenylalanine (L-DOPA). In addition, anti-ageing activities were determined through collagenase and elastase inhibitions. The results revealed that the ethanolic extract yielded the highest content, contained the highest phenolic content, and displayed the highest biological activities, including antioxidant, anti-tyrosinase, and anti-ageing effects (p < 0.05). This extract possessed the highest DPPH inhibition (57.0 ± 2.2%), equivalent concentration (EC1) (51.9 ± 0.7 mM FeSO4/g extract), Trolox equivalent antioxidant capacity (118.8 ± 0.9 mM Trolox/g extract), anti-tyrosinase activity on the conversion of L-tyrosine (26.4 ± 3.2%) and L-DOPA (27.1 ± 2.4%), anti-collagenase (65.4 ± 2.4%), and anti-elastase (68.3 ± 2.3%). Therefore, the ethanolic extract of M. integrifolia pericarp is a promising natural extract for use as antioxidant, anti-aging, and whitening active ingredient and is suggested for further cosmetic and cosmeceutical product development.