Antioxidant, Antibacterial Activities and Cytotoxicity of Garlic Leaf Extract from Garlic Waste

Five garlic parts (root, clove skin, leaf, flower stalk and garlic peel) of garlic waste from garlic harvest processing were used in this study. Each part of the garlic waste was screened for total phenolic, flavonoid and antioxidant activity after extraction with 70% ethanol. Interestingly, garlic leaf (GLf) showed the greatest richness of total phenolic, flavonoid and antioxidant activity. GLf was selected to extract with water and 70% ethanol and the highest extraction yield was achieved with water extract. The GLf extracts demonstrated a good quality standard of physical and chemical properties. The aqueous extract of GLf revealed the highest total phenolic content of 1,676.40 ± 18.02 mg GAE/100 g extract. Both aqueous and ethanolic extracts did not differ regarding total flavonoid contents, showing values of 118.60 ± 6.10 mg QUE/100 g extract and 110.90 ± 2.30 mg QUE/100 g extract, respectively. Phenolic compounds including gallic acid, catechin and tannic acid were detected in the aqueous and ethanolic extracts of GLf by HPLC assay. Moreover, four flavonoid compounds including isoquercetin, quercetin, kaempferol and rutin were detected in aqueous extract whereas the ethanolic extract presented apigenin, isoquercetin, quercetin and kaempferol. The ethanolic extract of GLf demonstrated the stronger antioxidant activity than aqueous extract. GLf extracts also exhibited antimicrobial activity against pathogenic bacteria with MIC and MBC values of 125-250 mg/mL. In addition, GLf aqueous extract showed lower toxicity on Vero cells than ethanolic extract. Therefore, GLf waste can be used as a cheap source of natural compounds and antioxidants, with potential applications in different biological, medicinal and food products. Keywords: Allium sativum L., Antibacteria, Antioxidant, Garlic, Toxicity