An innovative green extraction process for the development of traditional herbal drugs or food supplements

Abstract

Numerous plants are traditionally used in their fresh form in order to preserve the compounds within and avoid the risk of denaturation occurring during the drying process [1]. Usually, plant juice is obtained by squeezing the freshly harvested plant. Another way is to make an infusion or alcoholic tincture with fresh plant. For example, oat herb (Avena sativa L.) expressed juice is traditionally used for relief of mild symptoms of mental stress and to aid sleep (EMEA/HMPC/202966/2007). Purple coneflower herb (Echinacea purpurea (L.) Moench.) expressed juice also has a well-established use for the short-term prevention and treatment of common cold (EMEA/HMPC/104945/2006). However, during the pressing process, the plant cell walls can restrain the access and recovery of some interesting compounds. Furthermore, it releases enzymes which could potentially modify and alter these compounds: hydrolases, oxidases, de-glucosidases, etc. The adaptation of a twin-screw extrusion technology, mainly used in food industries for plant juice expression, allows us to obtain an enriched juice containing unadulterated compounds. Indeed, the combination of high pressure induced by the twin-screw rotation and rapid thermal treatment leads to complete destructuring of plant cell walls and an inhibition of enzyme activity, giving a juice with a higher yield and a higher active content. In purple coneflower juice, the level of caffeic acids (caftaric and cichoric acids) obtained by this technology is 0.79 mg/g of plant wet weight, whereas it is 0.0 mg/g by simple juice expression (due to polyphenoloxidases degradation [2]) and 0.12 mg/g of plant wet weight by water extraction at 100 °C.