Luteolin content and antioxidant activity in micropropagated plants of Poliomintha glabrescens (Gray)

Abstract

Mexican oregano is composed by a wide range of endemic species which support important economic activities, but with serious limitations. In this work a micropropagation protocol was established to regenerate oregano plants (Poliomintha glabrescens Gray) from apical buds. At the same time we evaluated the impact of this process in the phytochemical profile of the new plants. The optimal induction of apical buds was observed when shoot-tip explants were incubated on solidified Murashige and Skoog (MS) medium supplemented with 0.5 mg ml−1 α-naphthalenacetic acid (NAA) and 0.02 mg ml−1 6-benzyladenine. Also, the optimal response to root induction was with MS solid medium added with 0.5 mg ml−1 of NAA. The micropropagation protocol took 17 weeks with an efficiency of 40%, and plants achieved were successfully acclimatized under greenhouse conditions. The total phenolics (TP) concentration, antioxidant capacity (oxygen radical absorbance capacity, ORAC), and luteolin content from methanol extracts of wild type (WT) and in vitro (IN) and ex vitro (EX) plants were determined. The results show that TP content and ORAC were similar for WT and EX plants, but IN plants had the highest TP content and ORAC activity (25 and 28% respectively). Luteolin content showed significant differences between WT, IN and EX, with EX plants having the highest luteolin content (10% more compared to WT). In summary, we successfully microprogated oregano plants from WT and they contained similar amount of their TP content and ORAC activity and an increase in luteolin content.