Effects of plant growth regulators, mineral medium, and pH values on the callus induction of young stem cutting slices of Ehretia asperula Zoll. et Mor.

Xa den (Ehretia asperula Zoll. et Mor.) belongs to the Boraginaceae family, which is a precious medicine, called “cancer” tree in Muong at Hoa Binh province traditional medicine. Xa den was shown to inhibit the development of malignant tumors, reduce oxidation, enhance resistance... In this study, we investigated the induction of friable callus in Xa den young stem section that could be further used to the culture cell suspension and produce bioactive compounds. In that, we focussed on the effects of the plant growth regulators, mineral media, and pH on the formation of friable callus of Xa den. The results showed that all treatments stimulated the formation of callus from Xa den thin stem (0.5-1.0 mm). In particular, samples which were cultured in B5 medium supplemented with 0.4 mg/L 2,4-D and 0.1 mg/L BA, at pH 5.8 produced the highest percentage of secondary callus in friable (85%), and this callus also had highest fresh weight after 4 weeks of culture (0.054 g). To evaluate the presence of natural compounds in the callus and compared to those in cultivated plants, the ethanol extract of dry leaves, branches, and fresh callus were used. The results showed the presence of natural compounds in the callus such as organic acid, phenolic, tannin, alkaloid, and flavonoid was similar to the one in a 2-year-old plant.