Yabing Zou

Quinoa bran, a major by-product of quinoa processing, is rich in saponins but remains underutilized. In this study, a crude enzyme extract from Aspergillus niger sp.848 was employed for the biotransformation of quinoa saponins under controlled pH conditions (2.2 and 8.0). The transformation products were isolated by preparative HPLC and characterized by HR-MS and NMR. At pH 2.2, complete hydrolysis of both C-3 and C-28 glucosyl groups occurred, yielding 3-O-α-L-arabinopyranosyl phytolaccagenic acid (A1, a novel saponin) and 3-O-α-L-arabinopyranosyl hederagenin (A2). At pH 8.0, selective hydrolysis of only the C-3 glucosyl group produced 3-O-α-L-arabinopyranosyl phytolaccagenic acid 28-O-β-D-glucopyranosyl ester (B1) and 3-O-α-L-arabinopyranosyl hederagenin 28-O-β-D-glucopyranosyl ester (B2). The pH 2.2 transformation yielded 1.214 g total product from 2.0 g crude saponins (60.7% recovery), with isolated yields of 15.6% for A1 and 22.9% for A2. The pH 8.0 transformation gave 1.078 g total product (53.9% recovery). This pH-switchable biotransformation process enables the targeted production of structurally distinct saponin derivatives from quinoa bran, offering a sustainable approach for the valorization of this agro-industrial by-product into bioactive saponin derivatives with potential as functional food ingredients.

Quinoa bran, a major by-product of quinoa processing, is rich in saponins but remains underutilized. In this study, a crude enzyme extract from Aspergillus niger sp.848 was employed for the biotransformation of quinoa saponins under controlled pH conditions (2.2 and 8.0). The transformation products were isolated by preparative HPLC and characterized by HR-MS and NMR. At pH 2.2, complete hydrolysis of both C-3 and C-28 glucosyl groups occurred, yielding 3-O-α-L-arabinopyranosyl phytolaccagenic acid (A1, a novel saponin) and 3-O-α-L-arabinopyranosyl hederagenin (A2). At pH 8.0, selective hydrolysis of only the C-3 glucosyl group produced 3-O-α-L-arabinopyranosyl phytolaccagenic acid 28-O-β-D-glucopyranosyl ester (B1) and 3-O-α-L-arabinopyranosyl hederagenin 28-O-β-D-glucopyranosyl ester (B2). The pH 2.2 transformation yielded 1.214 g total product from 2.0 g crude saponins (60.7% recovery), with isolated yields of 15.6% for A1 and 22.9% for A2. The pH 8.0 transformation gave 1.078 g total product (53.9% recovery). This pH-switchable biotransformation process enables the targeted production of structurally distinct saponin derivatives from quinoa bran, offering a sustainable approach for the valorization of this agro-industrial by-product.