Comparison of the effect of extraction methods on waste cotton (Gossypium hirsutum L.) flowers: metabolic profile, bioactive components, antioxidant, and α‐amylase inhibition

Waste cotton flowers, as a by-product of cotton cultivation, are enriched with bioactive substances that render them a promising natural source of health-promoting benefits. In this study, ultrasound-assisted extraction (UAE), subcritical water extraction (SWE), and conventional extraction (CE) approaches were applied to extract bioactive compounds from waste cotton flowers, and the metabolic profiles, bioactive components, antioxidants, and α-amylase inhibition of different extractions were systematically analyzed and compared.It was observed that UAE and CE extracts had similar metabolic profiles compared with SWE. The flavonoids and amino acids and derivatives were more prone to be extracted by UAE and CE, whereas phenolic acids tended to accumulate in SWE extract. The UAE extract had the highest amounts of total polyphenols (214.07 mg gallic acid equivalents per gram dry weight) and flavonoids (33.23 mg rutin equivalents per gram dry weight) as well as the strongest inhibition on oxidation (IC50 = 10.80 μg mL-1 ) and α-amylase activity (IC50 = 0.62 mg mL-1 ), indicating that chemical composition was closely related to biological activity. Additionally, microstructures and thermal behaviors of the extracts were investigated and highlighted the ability of UAE.Overall, it can be concluded that UAE is an efficient, green, and economical extraction method to produce bioactive compounds from cotton flowers, and the UAE extracts could be used in food and medicine industries because of their high antioxidant and α-amylase inhibitory activity. This study provides a scientific basis for the development and comprehensive utilization of cotton by-products. © 2023 Society of Chemical Industry.