Physicochemical Properties and Antioxidant Capacities of Different Parts of Ginger (Zingiber officinale Roscoe)

The physicochemical characteristics and antioxidant activities of leaf, stem, and root of ginger (Zingiber officinale R.) were determined. Nutrient composition, reducing sugar, saponin, mineral, heavy metal, total phenolic and total flavonoid contents, and antioxidant activities based on DPPH radical scavenging and FRAP assay were measured. Catechins, gingerols, shogaols, and capsaicin compositions were also determined by HPLC. The contents of water, proteins, fats, carbohydrates, fiber, and ash from ginger root were 6.4, 6.8, 3.2, 65.4, 7.3, and 18.2%, respectively. Crude fiber contents of leaf and stem were 4¢¦5 times higher than those of root (P0.05), and reducing sugar content of stem was about 3 times higher than those of root. Crude saponin contents were in the order of stem root leaf, and saponin content of leaf was 1.7 times higher than that of root (P0.05). Mineral contents and composition varied among different parts, and Ca contents of leaf and stem were 5 times higher than that of root. The 6-gingerol, 10-gingerol, and 8-shogaol contents of leaf and stem were identified by HPLC, and 8-shogaol content of leaf was 5 times higher than that of root (P0.05). The major fatty acids in ginger were palmitic acid, oleic acid, linoleic acid, and linolenic acid. Lauric acid was only detected in root, arachidic acid was not detected in stem, and the linoleic acid content of leaf was 5 times higher than that of root. The total catechin content of methanol extract was in the order of root leaf stem, and stem was about 30 times higher than that of root. Antioxidant activity was highly correlated with total phenolic and total flavonoid contents. Based on these experiments, it can be concluded that leaf, stem, as well as root of ginger can be used as natural preservatives, and they can be developed as healthy foods due to their antioxidant activities and abundant polyphenols. This study suggests that the whole ginger plant, including root, leaf, and stem, might be new functional vegetables.