Antimicrobial and Antioxidant Activities of 18β-Glycyrrhetinic Acid Biotransformed by <i>Aspergillus niger</i>

The search for novel plant-based antioxidant and antibacterial medication has garnered a lot of attention lately. <i>Glycyrrhiza glabra</i>, known as licorice, is one of the most important medicinal plants. The primary component of Glycyrrhiza glabra is glycyrrhizin, which is biotransfor...

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Main Authors: Shaymaa Wagdy El-Far, Mahmoud A. Al-Saman, Fatma I. Abou-Elazm, Rania Ibrahim Shebl, Asmaa Abdella
Format: Article
Language:English
Published: MDPI AG 2024-09-01
Series:Microbiology Research
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Online Access:https://www.mdpi.com/2036-7481/15/4/133
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Summary:The search for novel plant-based antioxidant and antibacterial medication has garnered a lot of attention lately. <i>Glycyrrhiza glabra</i>, known as licorice, is one of the most important medicinal plants. The primary component of Glycyrrhiza glabra is glycyrrhizin, which is biotransformed into 18α- and 18β-glycyrrhetinic acid for a variety of medicinal purposes. The goal of this study was to improve the bioavailability of glycyrrhizin by its biotransformation into glycyrrhetinic acid by <i>Aspergillus niger</i>. The biotransformation process was optimized using response surface methodology. A two-level Plackett–Burman design was employed to identify the factors that had a significant impact on the process of biotransformation. The three main variables were pH, glycerrhizin concentration, and incubation time. These three medium components were further optimized using a 3-level Box–Behnken design, and their optimum levels were pH of 8, an incubation period of 6 days, and a glycyrrhizin concentration of 1%. Using these optimum conditions, the maximum level obtained was 159% greater than in the screening experiment. Regarding the antimicrobial activity of glycyrrhizin extract, <i>Bacillus subtilis</i> emerged as the most sensitive organism with the lowest MIC (60 µg/mL) and the highest zone of inhibition (17 mm). The most resistant organism was <i>Pseudomonas aeruginosa</i>, which had the highest MIC (400 µg/mL) and the smallest zone of inhibition (10 mm). In the case of glycyrrhetinic acid, <i>Bacillus subtilis</i> was the most sensitive organism with the highest zone of inhibition (32 mm) and the lowest MIC (20 µg/mL). <i>Pseudomonas aeruginosa</i> was the most resistant organism, with the lowest zone of inhibition (18 mm), and the highest MIC (140 µg/mL). The antioxidant activity of glycyrrhizin extract increased from 12.81% at a concentration of 63 µg/100 µL to 41.41% at a concentration of 1000 µg/100 µL, while that of glycyrrhetinic acid extract increased from 35.5% at a concentration of 63 µg/100 µL to 76.85% at a concentration of 1000 µg/100 µL. The present study concluded that biotransformation of glycyrrhizin into glycyrrhetinic acid increased its bioavailability and antioxidant and antimicrobial activities. Glycyrrhizin and glycyrrhetinic acid might be used as a natural antimicrobial and antioxidant in pharmaceutical industries
ISSN:2036-7481