Soyasapogenol B, an aglycone part (non-sugar) of group B soyasaponin, pentacyclic triterpenoids (PTs) [1], [2], [3], [4], [5], [6] widely distributed in various medicinal plant, such as Glycine max (soybean) and Pisum sativum (Peas) [7], [8] has attracted significant attention due to its broad range of pharmacological properties, including anti-inflammatory, hepatoprotective, and anticancer activities [9], [10], [11], [12], [13], [14], [15], [16]. Unlike its other saponin precursor, which can impart undesirable bitter and off-flavors, Soyasapogenol B exhibits slightly better solubility and bioavailability [17], [18], [19], [20]. However, its therapeutic potential remains restricted, necessitating structural modifications to overcome these limitations.

Microbial biotransformation has emerged as a powerful tool in natural product synthesis, enabling highly selective and sustainable transformations under milder reaction conditions [21], [22], [23], [24]. It is a versatile strategy, utilizing multi-step modifications and diverse enzymatic reactions with remarkable efficiency, unlike traditional chemical synthesis, which often requires toxic reagents, high temperatures, and generates hazardous waste. Therefore, they are ideal for the structural diversification of bioactive compounds [25], [26]. For instance, Penicillium griseofulvum and Streptomyces griseus have been reported for their intrinsic biocatalytic activities, including deglycosylation as well as site-selective oxidation mediated through cytochrome P450 enzymes [27], [28], [29], [30], [31], [32], [33]. Interestingly, our previous work has also demonstrated their proficiency in introducing functional groups via regio- and stereoselective reactions on various PTs compounds, yielding novel derivatives with enhanced pharmacological properties [34], [35], [36], [37].

Aligning with our longstanding research this study aimed to investigate the biocatalytic capability of Streptomyces griseus ATCC 13273 and Penicillium griseofulvum CICC 40293 in generating novel metabolites from Soyasapogenol B (1). Through comprehensive structural analysis using nuclear magnetic resonance (NMR) techniques, we successfully identified ten unique metabolites exhibiting distinct structural modifications. Thus, this work reflects our ongoing initiative in the biotransformation studies of various saponins in oil crops and establishes a robust microbial-based strategy for the structural diversification of Soyasapogenol B. Ultimately, this approach highlights the potential to create novel libraries of triterpenoid derivatives for drug discovery while providing insights into the underlying enzymatic mechanisms.