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Ruta chalepensis, a medicinal plant, produces biologically active coumarins (CRs) and furanocoumarins (FCRs). However, their yield is quite low in cultivated plants. In this work, the influence of light-emitting diodes (LEDs) was investigated on the accumulation of CRs and FCRs in the callus cultures and field-grown plants of R. chalepensis. Among the various tested wavelengths of LED lights, maximum accumulation of CR and FCRs was recorded under blue LED treatment in both the callus cultures as well as field-grown plants when compared with respective controls treated with white LED. Metabolite analyses of LED-treated field-grown plants showed that highest concentrations of CR (umbelliferone, 2.8-fold), and FCRs (psoralen, 2.3-fold; xanthotoxin, 3.8-fold and bergapten, 1.16-fold) were accumulated upon blue LEDtreatment for 6 days. CR and FCRs contents were also analyzed in the blue LED-and red LED-treated in vitro callus tissue. Upon blue LED-treatment, callus accumulated significantly high levels of umbelliferone (48.6 AE 1.2 µg g À1 DW), psoralen (370.12 AE 10.6 µg g À1 DW) and xanthotoxin (10.16 AE 0.48 µg g À1 DW). These findings imply that blue LED-treatment is a viable option as a noninvasive and lowcost elicitation technology for the enhanced production of biologically active CR and FCRs in field-grown plants and callus cultures of R. chalepensis.

Piper betle leaves possess several ethnomedicinal properties and are immensely used in traditional medicinal practices in regions of Asian and African subcontinents.

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