Enhancement of total antioxidants and flavonoid (quercetin) by methyl jasmonate elicitation in tissue cultures of onion (Allium cepa L.)

The onion (Allium cepa) is a vegetable used extensively all over the world both for culinary purposes as well as in medicine. Its medicinal values are due to the high levels of biologically-active compounds present within the bulb. There are various phytochemicals of therapeutic importance found in A. cepa. Quercetin, a flavonoid, is one of these phytochemicals and it is a potent antioxidant. Allium cepa is a dietary supplement and is beneficial for diverse ailments, thus justifying its status as a valuable medicinal plant. Due to its medicinal significance, elicitation of total antioxidants and quercetin levels have been attempted to enhance their production in tissue callus cultures. This study reports in vitro enhancement of total antioxidants and quercetin in A. cepa using methyl jasmonate as an elicitor. A reverse phase-high performance liquid chromatography (RP-HPLC) method was used with an isocratic system and a flow rate of 1.0 mL min−1 and a mobile phase of acetonitrile: 1% v/v acetic acid (60%:40% v/v). The detection wavelength was 362 nm and the retention time 8.79 minutes. Total antioxidant and quercetin contents were maximal with 100 µM of methyl jasmonate in leaf tissue callus cultures at 84.61 ±6.03% and 0.81 ±0.03 mg g−1 dry cell weight, respectively. They decreased with further increases of methyl jasmonate at 200 µM. The increase in total antioxidant and quercetin contents were 2.3- and 13.9-fold, respectively. The optimization of methyl jasmonate as an elicitor, as well as the determination of a suitable concentration in A. cepa in callus cultures, will be helpful for enhanced production of various other secondary metabolites of therapeutic significance. This could be beneficial for the pharmaceutical and neutraceutical industries for herbal drug formulations.