Ultrasonic extraction of reducing sugar and polyphenols from burdock (Arctium lappa L.) root waste and evaluation of antioxidants and α-glucosidase inhibition activity

Ultrasonication is a potential and highly efficient green technique to extract bioactive elements from plants. In this study, ultrasonication technology is used to extract reducing sugar and polyphenolic compounds from burdock root waste (Arctium lappa L.) using the response surface approach. For this, the ultrasonic extraction parameters, solid-to-water ratio (20-40 g/mL), sonication time (60-100 min), and sonication temperature (40-60 degrees C) were optimized through response surface methodology (RSM), where the reducing sugar and total phenolic content were selected as the responses. The results indicated that all the parameters considered had a significant impact (p<0.05) on reducing sugar (ranging from 4.38 to 6.12%) and total phenolic content (ranging between 4.94 and 6.98 mg GAE/g). The optimized condition was solid to liquid ratio of 38.52 g/mL, sonication time of 90.06 min, and sonication temperature of 59.86 degrees C, which predicted reducing sugar of 6.12% (6.48% after validation) and total phenolic content of 7.04 mg GAE/g dw (7.44 mg GAE/g dw after validation). Furthermore, in vitro biological activities of burdock root extracts exhibited excellency in retaining the reducing sugar (6.48-6.97%), total flavonoid content (40.66-42.36 mg RE/g), DPPH (33.70-43.45 mu mol TE/g), and ABTS(+) (28.10-29.83 mu mol TE/g) radical scavenging activity, ferric-reducing antioxidant power (54.53-58.70 mu mol TE/g), and a-glucosidase inhibitory activity (>20%) both in ultrasonic and conventionally extracted samples with ultrasonication showed the higher activity. The results suggest that ultrasonication is an effective green technology and that burdock root waste has significant antioxidant and antidiabetic potential and could be used as a promising source of functional components.