Effects of shading on synthesis and accumulation of polyphenolic compounds in ginger (Zingiber officinale Roscoe) varieties

Abstract

Extracts of leaves and rhizomes of two varieties (Halia Bara and Halia Bentong) of Malaysian young ginger (Zingiber officinale) grown under different shade net (0 and 60%) were examined as potential sources of phenolics and flavonoids compounds for antioxidant activities. High performance liquid chromatography (HPLC) with UV detection was employed for the identification and quantification of the polyphenolic compounds (flavonoids and phenolic acids). Flavonoid compounds (quercetin, apigenin, luteolin, and myricetin) and phenolic acids (gallic acid, vanillic acid, ferulic acid, tannic acid and caffeic acid) were identified with different concentration in leaves and rhizomes of ginger varieties. The most abundant phenolic acid in ginger was gallic acid, and flavonoids were quercetin and apigenin. Accordingly, accumulations of flavonoids in the leaves were high under 60% shade, while most phenolic acids were observed in the rhizomes under 0% shade. Furthermore, caffeic acid was only detected from ginger grown under 0% shade, while tannic acid only accumulated in the leaves of ginger grown under 60% shade level. The results indicated phenolic acids and flavonoids absolutely light dependent and them biosynthetic rate is related to light intensity. Additionally, this study also validated Halia Bara and Halia Bentong medicinal potential based on polyphenolics compound. Key words: High performance liquid chromatography, shade, flavonoids, phenolic acids, Halia Bentong, Halia Bara.