Water-Based and alternative extraction techniques for stilbenoids from grape cane: A comparative study

Grape cane is a viticultural byproduct rich in bioactive stilbenoids and other phenolic compounds. Valorization of grape cane relies on effective extraction methods, traditionally using ethanol. This study aimed to compare a series of extraction techniques, including an extraction based on various ethanol–water mixtures as well as water-based methods combined with ultrasound-assisted extraction and microwave-assisted extraction. In this study, water-based extraction led to stilbenoid extraction yields determined by HPLC-DAD analyses that were significantly lower, even when applying ultrasound (43 mg/kg grape cane), than those obtained with 80 % ethanol maceration (4373 mg/kg). Water-based extraction utilizing microwave heating at optimal conditions (100 °C, 20  min) allowed yields of about 555 mg/kg. The spectrophotometrically measured total phenolic content showed a similar trend, with the highest yield achieved at 100 °C for 20 min under microwave-assisted extraction (13 g GAE /kg), remaining notably lower compared to using 80 % ethanol (20 g GAE /kg). These findings highlight the potential of increased temperature water-based extraction methods but also underscore the need for further optimization. Future research should aim to refine these techniques and explore more advanced methods, such as subcritical or high-pressure water extraction, to enhance the valorization of grape cane and support its use in producing bioactive extracts.