A functional food ingredient featuring immune-enhancing and antioxidant properties: Buddleja officinalis Maxim polysaccharide (BOM0.05S2)

Natural plant polysaccharides with high biological activity are highly anticipated in the food manufacturing industry; however, their extraction remains challenging due to low efficiency. BOM0.05S2 is a pectin-like polysaccharide (13.6 kDa) isolated from Buddleja officinalis Maxim, enriched with galacturonic acid, mannose, and glucose. Herein, the extraction of crude polysaccharides from B. officinalis (BOMs) was optimized using a Box-Behnken design coupled with response surface methodology. This approach considered four factors (extraction time, liquid-to-material ratio, extraction temperature, and number of extractions) at three levels, resulting in optimal conditions of 1:25 g·mL⁻¹, 90.2°C, 3.96 h, and 4 extractions. The actual yield of crude polysaccharides was 7.28 ± 0.11 %. Subsequently, BOM0.05S2 was further purified from BOMs, achieving a final yield of approximately 1.82 %, which surpasses the previously reported yield of 0.99 %. The chemical characteristics, antioxidant activity, and immune-enhancing effects of BOM0.05S2 were thoroughly evaluated. BOM0.05S2 demonstrated anti-hemolytic properties on red blood cells, exhibited significant scavenging activities against DPPH and hydroxyl radicals in vitro, and markedly enhanced the production of NO and TNF-α in macrophages in a dose-responsive manner. These findings suggest that BOM0.05S2, with their potent antioxidant activity and immune-enhancing properties, hold great promise for application as functional food ingredients in the food and pharmaceutical industries.