Biological and Chemical Stability of Garlic-Derived Allicin

Abstract

This study verifies the instability of garlic (Allium sativum L.)-derived allyl 2-propenylthiosulfinate (allicin) in various aqueous and ethanolic solutions as well as in vegetable oil through chemical and biological analyses performed simultaneously. Crushed fresh garlic cloves generated antibacterial activity and chemically detectable allicin, a major antibacterial principle, and both declined on a daily basis in aqueous and ethanolic solutions at room temperature, showing biological and chemical half-lives of about 6 and 11 days, respectively. Allicin was more stable in 20% alcohol than in water, but surprisingly unstable in vegetable oil, with an activity half-life 0.8 h, as estimated from its antibacterial activity toward Escherichia coli, and a chemical half-life of 3.1 h, based on chromatographic quantification. In alcoholic and aqueous extracts, the biological half-life of allicin tended to be longer than the chemical one, suggesting the occurrence of bioactive compounds other than allicin in the extracts.

A Comparative Study on the Total Antioxidant and Antimicrobial Potentials of Ethanolic Extracts from Various Organ Tissues of <i>Allium</i> spp.

“…Then 50 μL of 1 mg·mL −1 Allium extract were applied to an ethanol-sterilized paper disc (8 mm in diameter), and were placed on the plate. After incubation at 37˚C for 24 h, the inhibition zone around the disc was measured [6]. Penicillin and tetracycline were used as reference controls in the antimicrobial assay.…”

“…The experiments were run in triplicate, and the developing inhibition zones were compared with those of the reference discs. In addition, the minimal inhibitory concentration (MIC) of the samples was determined by the broth dilution method using the serially diluted Allium extracts as described [6,9]. Then, bacterial cultures were prepared in a nutrient broth and incubated at 37˚C for 24 h. The bacterial cultures were adjusted with sterilized saline to bring the concentration to 10 7 mL −1…”

“…However, it was found in our experiments that the hot water extracts contain many visible remnants of plants, and that their antioxidant and antimicrobial activities were less than those of the ethanolic extracts (results not shown). Ethanol has been proved to be a better solvent than water for the extraction of allicin in plant tissues [6]. The subsequent extraction of Allium spp.…”

“…However, the Allium extracts showed higher inhibitory responses towards B. cereus, S. aureus and P. aeruginosa, but they were less effective in inhibiting E. coli. The mechanisms as how natural compounds in green onion and garlic exert their function have been previously discussed and the antimicrobial activity of the allicin contained in the garlic and the onion has been proposed in many studies [6,[24][25][26]. The sulfur-containing compounds, such as allicin contained in green onion and garlic, could be responsible for the antimicrobial potential.…”

“…This area, mostly run by local small-scale farmers, is famous for its top-quality, fragrance-rich green onions. Green onions and garlic are commonly consumed vegetables that possess markedly bioactive potentials, such as antioxidant capacity [4], antimicrobial activity [5,6], antiplatelet activities [7] and anticancer activity [8]. With successful demonstration of the functioning properties of the Sunshin green onions, this study would help the local farmers to market their produce with value adding strategies and benefit economically from their production.…”