Proximate Composition, Phytochemical Analysis and In Vitro Antioxidant Potentials of Zingbier Officinale Roscoe Varieties

Lim, Mei San (2018) Proximate Composition, Phytochemical Analysis and In Vitro Antioxidant Potentials of Zingbier Officinale Roscoe Varieties. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

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Abstract

Ginger (rhizome of Zingiber offinale Roscoe) is an excellent source of several bioactive phenolics. They exhibit a variety of biological activities, such as anti-oxidant, anti-inflammatory, antimicrobial, anticancer, anti-emetic and being intensively studied to evaluate their beneficial effects on health. The objectives of the present study were to determine the proximate composition, phytochemical analysis and in vitro antioxidant potentials in rhizomes of Zingiber offinale Roscoe var. Karak ginger (KG), var. Bentong ginger (BG), and var. Thai ginger (TG). Proximate analysis of ginger was carried out using AOAC method. The moisture content and ash content of proximate analysis was determined from fresh rhizomes. The moisture content of fresh KG, BG and TG were 75.4%, 78.8% and 88.8 %, respectively. The ash content of fresh KG, BG and TG has no significant difference. In addition, the percentage of crude protein and fiber in three varieties of rhizomes were significantly different (P<0.05) from each other with KG having the highest percentage of crude protein and fiber. The carbohydrate percent in BG was significantly higher (P<0.05) than the other two rhizomes. In contrary, the crude lipid percent of TG was the highest among three varieties of ginger. Ethanolic extracts of ginger were investigated for their antioxidant properties using 2, 2-diphenyl-2-picryl hydrazyl (DPPH) assay and ferric reducing antioxidant power (FRAP) assay. Total phenolic content and total flavonoid content of rhizomes were also analysed by using Folin-Ciocalteu method and aluminium chloride colorimetric method due the association between phytochemical constituents and antioxidant activities. The results showed that total phenolic contents were 411.333, 224.667, and 111.333 of mg GAE/g DM for KG, BG and TG, respectively. Total flavonoid content of KG, BG, TG rhizomes were 108.533, 75.200 and 39.200 of mg CE/g DM, respectively. The total phenolic, flavonoid content and reducing power were differed significantly (P<0.05) among three varieties of rhizomes. There is no significant different between free scavenging capacity of BG and TG, but the ascorbic acid equivalent capacity(AEAC) of DPPH assay showed that KG (0.488) possessed the higher antioxidant capacities than BG (0.274) and TG (0.232) and thus could be potential rich natural antioxidants. Analysis of different concentration of [6]-gingerol standards generated a calibration curve for the identification and quantification of [6]-gingerol in ginger extract by using gradient elution reversed-phase UPLC method. The [6]-gingerol concentration of KG, BG and TG were 112.978, 39.521, and 23.384 of μg/ml, respectively. This showed that the concentration of [6]-gingerol was aligned with antioxidant properties as KG contain both significant higher (P<0.05) [6]-gingerol concentration and antioxidant properties than BG and TG. The results could contribute to the on-going researches in setting benchmark for identification of different ginger varieties. Keywords: Karak ginger (KG), Bentong ginger (BG), Thai ginger (TG), Proximate composition, antioxidants, phenolic, flavonoid, [6]-gingerol