Phytochemical profile and antioxidant activity of various solvent extracts of two varieties of ginger and garlic

Abstract

There is limited information on the phytochemical profile and antioxidant activity of ginger and garlic consumed in Uganda. This could have an impact on its widespread use and industrial application. Thus, this study was done to determine the phytochemical profile and antioxidant activity of two varieties of ginger and garlic commonly consumed in Uganda. Fresh ginger rhizomes and garlic cloves of "local" and "hybrid" varieties were acquired from a local food market, washed, grated, and extracted using acetone, ethanol, methanol, and water. Standard techniques were used to determine the phytochemical composition. Total phenolic and flavonoid content were measured using Folin-Ciocalteu and aluminium chloride assays, respectively. Antioxidant activity was determined using the 2, 2-Diphenyl-1-picryl hydrazyl (DPPH) assays. Ginger extracts exhibited significantly higher total phenolic and flavonoid content compared to garlic (p˂0.05). The highest total phenolic and flavonoid content was in ethanol and methanol extracts of local ginger: 1968.49 and 2172.65 mg GAE/100 g; 254.24 and 184.62 mg QE/100 g, respectively. Tannins, alkaloids, saponins, and terpenoids were in varying concentrations in the extracts. Levels of Vitamin C were significantly high in aqueous extracts (p˂0.05), 38.34 and 40.80 AAE/100 g in local and hybrid ginger; 33.65 and 35.24 mg AAE/100 g in local and hybrid garlic, respectively. The free radical scavenging activity of extracts varied depending on concentration, with a strong positive correlation between antioxidant activity and total phenolic and flavonoid content. The half maximal inhibitory concentration (IC50) ranged from 0.16 to 8.93 mg/ml in local ginger, 4.43-6.44 mg/ml in hybrid ginger, 3.93-5.64 mg/ml in local garlic, and 4.44-5.27 mg/ml in hybrid garlic. The best antioxidant activity was exhibited by ethanol extracts of the local ginger. According to the findings, the two varieties of ginger and garlic have strong antioxidant activity due to their different phytochemical compositions, which could make them useful as natural antioxidants in food and medicine applications.

Keywords: Flavonoids; Inhibitory concentration; Natural antioxidants; Phenolic.

Fig. 1

DPPH free radical scavenging ability of Ginger extracts in varying concentration. Values plotted is the mean of triplicate determination, different superscripts at the same concentration denote significant difference in inhibition percentage (p˂0.05).

Fig. 2

DPPH free radical scavenging ability of Ginger extracts in varying concentration. Values plotted is the mean of triplicate determination, different superscripts at the same concentration denote significant difference in inhibition percentage.

Fig. 3

Relationship between IC 50 and Total phenolic content of ginger extracts. Values with the different superscript letters across the line are significantly different (p˂0.05).

Fig. 4

Relationship between IC50 and total phenolic content of garlic extracts. _{Values with different superscript letters along the line are significantly different (p˂0.05).}