Elevation of secondary metabolites production through light-emitting diodes (LEDs) illumination in protocorm-like bodies (PLBs) of Dendrobium hybrid orchid rich in phytochemicals with therapeutic effects

Gas-chromatography-mass-spectrometry revealed the presence of various bioactive compounds with anticancer properties in protocorm-like-body (PLB) cultures of a Dendrobium hybrid orchid (Dendrobium Enopi x Dendrobium Pink Lady). Pre-illumination of red fluorescent light lessened the stimulating effects of light-emitting diodes (LEDs) on secondary metabolites production among in vitro PLB cultures, possibly due to habituation. The highest flavonoid content of 16.79 μmol/ g of fresh weight (FW) was achieved under blue-red (1:1) LED for PLBs pre-treated with white LED for more than 3 subculture cycles. Phenolics content significantly reduced as PLBs pre-cultured under red fluorescent light for 2 subculture cycles were exposed to LED illuminations, where far red LED resulted in the lowest total phenolic content (18.85 μmol/ g FW). High intensity green LED (16.9 μmol/s) enhanced the accumulation of phenolics while amino acids such as L-leucine, glycine and proline exhibited no significant stimulating effect for secondary metabolites production.

Keywords: Bioactive compounds; DDMP, 4H-Pyran-4-one, 2,3-dihydro-3,5-dihydroxy-6-methyl; GCMS, Gas chromatography-mass spectrometry; GSH, Reduced glutathione; Habituation; LED, Light-emitting diode; Light-emitting diodes; NF-KB, Nuclear factor kappa B; PAL, Phenylalanine ammonia-lyase; PLB, Protocorm-like bodies; Phenolics; Protocorm-like-body; ROS, Reactive oxygen species.