Insect pollination effects on antioxidant content of Perilla frutescens seeds analyzed by NMR spectroscopy

The importance of perilla frutescens as a species rich in medicinal properties and with a high antioxidant content is increasingly know. The use of this asian plant is spreading worldwide. Our previous studies regarding visits by honey bees and other insect pollinators on Perilla aimed to explore the possible effects on the pollinator action on the content of active ingredients of seeds from this species . The positive effects of pollinating insects and in particular the honey bee, are well known in crop plants such as fruit, oilseed and fodder, but have not been studied in medicinal plants. Pollination tests were conducted in september (2013) by isolating plants of Perilla with mesh cages before blooming and considering another plants left open to insect pollination. At maturity, seeds were collected counted and weighed. In (2015) additional trials were carried out to assess possible differences in antioxidant content of open pollination plants. The difference in seeds number and weight between open pollinated flowers recorded using a 600 MHz spectrometer showed the presence of rosmarinic acid, luteolin and apigenin, in line with previous studies, while their content was increased in plants with open insect pollination. In particular seeds from open (2013) compared to caged plants indicated the presence of glucosylated flavonoid, most likely due the proteolitic activity of glucosidic enzymes. Seeds from open-pollinated (2015) plants showed a content of luteolin and epigeninthat was increased by 3-fold compared to self-polinated (2013) plants. As he honey bee is the main pollinator of Perilla, its important role in increasing the presence of antioxidants is becoming more evident.