Activity-guided fractionation based on in vitro assays was used to identify antibacterial components in the residue wasted in the manufacturing process of aged garlic extract (AGE). Antimicrobial activity of the hexane extract of aged garlic-derived residue (AGR) was evaluated against clinically isolated Gram-positive and -negative bacteria including levofloxacin (LVX)-resistant strains. Among antimicrobial fractions separated from the hexane extract of AGR, several polysulfides, such as diallyl-tetrasulfide (DAS₄), -pentasulfide (DAS₅) and -hexasulfide (DAS₆), were identified as active components, whose chemical structures were determined by means of LC–MS and NMR spectroscopy. We found that those sulfides exhibited antimicrobial activities against Gram-positive bacteria at minimum inhibitory concentrations (MICs) ranging from 32 to 80 μg/mL. Although these sulfides were less active than LVX against most of the bacteria examined, they were more potent against Staphylococcus aureus (S. aureus) including methicillin-resistant S. aureus (MRSA). Surprisingly, DAS₅ significantly suppressed the biofilm formation of S. aureus by 60% at a concentration of 1.25 μg/mL, which is extremely lower than its MIC value. These results show that AGR contains several antimicrobial diallyl-polysulfides which have the potential to inhibit the growth and biofilm formation of bacteria and AGR may be a useful bioresource as a natural additive for antibiotic drugs or foods.

中文翻译：

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大蒜加工厂排放的残留物中抗菌成分的鉴定和测定

基于体外测定的活性指导分级分离用于鉴定在老化大蒜提取物（AGE）生产过程中浪费的残留物中的抗菌成分。评估了老化大蒜衍生残渣（AGR）的己烷提取物对临床分离的革兰氏阳性和阴性细菌（包括耐左氧氟沙星（LVX）的菌株）的抗菌活性。从AGR的己烷提取物中分离出的抗菌组分中，有几种多硫化物，例如二烯丙基四硫化物（DAS ₄），-五硫化物（DAS ₅）和-六硫化物（DAS _6））被鉴定为活性成分，其化学结构通过LC-MS和NMR光谱测定。我们发现这些硫化物在32至80μg/ mL的最低抑菌浓度（MIC）下对革兰氏阳性细菌表现出抗菌活性。尽管这些硫化物对大多数受检细菌的活性低于LVX，但它们对包括耐甲氧西林的金黄色葡萄球菌（MRSA）的金黄色葡萄球菌（S. aureus）更有效。令人惊讶的是，DAS ₅显着抑制了金黄色葡萄球菌的生物膜形成。浓度为1.25μg/ mL时可降低60％，远低于其MIC值。这些结果表明，AGR含有多种抗菌二烯丙基多硫化物，具有抑制细菌生长和生物膜形成的潜力，并且AGR作为抗生素或食品的天然添加剂可能是有用的生物资源。