Comparative study of microwave-vacuum and vacuum drying on the drying characteristics, dissolution, physicochemical properties, and antioxidant capacity of Scutellaria extract powder

Scutellariae Radix (Labiatae family) is the dried root of Scutellaria baicalensis Georgi, which is sometimes referred to as Huang Qin in Chinese. This root is an important traditional medicine in Asia to treat inflammatory and allergic diseases. Scutellaria extract is prepared from Scutellariae Radix, and it is an important intermediate for the preparation of many traditional Chinese medicine agents. For the preparation of Scutellaria extract, drying is an indispensable process, and two different drying methods, microwave-vacuum and vacuum drying, have been adopted in practical production. However, the effect of the two different drying methods on the physicochemical properties and biological activity of Scutellaria extract are largely unknown. Thus, in this paper, the drying kinetics and curve, the dissolution, the physicochemical properties and the antioxidant activity were assessed to evaluate the effect of the two different drying methods on Scutellaria extract powder. The results indicated that the microwave-vacuum drying has a significantly shorter drying time (9 to 13 min), a higher dissolution (34 +/- 1.5%), a lower hygroscopicity (16.04 to 17.22%), a better flowability (the repose angle was 45.7 +/- 12 degrees to 46.6 +/- 2.5 degrees, compression degree was 38.7 +/- 1.1 to 40.2 +/- 0.6%) and formability (the tensile strength was 1.66 +/- 0.07 to 1.83 +/- 0.41 MPa), as well as higher antioxidant capacity (IC50 was 11.3 +/- 0.5 to 11.8 +/- 0.8 mu B), than those of vacuum drying (130 to 150 min, 32 +/- 13%, 19.74% to 20.02%, 482 23 to 49.7 +/- 2.2, 51.6 +/- 1.4% to 53.7 +/- 1.9%, 1.57 +/- 0.20 to 1.60 +/- 0.36 MPa, 13.5 +/- 0.9 to 13.9 +/- 0.8 mu g) (P< 0.05). However, the parameters of the two different drying methods had no significant effect on these indexes (P> 0.05). Thus, microwave vacuum drying might be a good method for drying Scutellaria extract. (C) 2017 Elsevier B.V. All rights reserved.