Enhancement of Antioxidant Activity and Bioactive Compounds in Eggplants Using Postharvest LEDs Irradiation

Abstract

Eggplant (Solanum melongena L.), one of the major vegetable crops, is recognized for its availability of numerous bioactive compounds and antioxidant activity. The accumulation of these compounds in plant tissues can be increased by exogenous stimuli, including light exposure. This study aimed at enhancing the antioxidant activity and bioactive compounds of eggplant using light-emitting diode (LEDs) irradiation after harvest. For this purpose, eggplant fruits were irradiated under LEDs at different wavelengths, including red (650–660 nm), blue (450–460 nm), or the combination of red and blue (red + blue) LEDs, for 48 h. The results indicated that red + blue LED exposure during postharvest significantly (p < 0.05) elevated the accumulation of bioactive compounds and antioxidant activity. The accumulation of major phenolic compounds, chlorogenic acid (58.59 mg/100 g FW), and gallic acid (14.25 mg/100 g FW) in the eggplant fruits was increased significantly under red + blue irradiation when compared with the control (under dark condition). The total phenolic (821.86 mg GAE/100 g FW) and the total flavonoid (595.98 mg CE/100 g FW) contents were shown to have a considerably high accumulation in the peels of eggplant after irradiation under red + blue LEDs, whereas the total carotenoid content was relatively high in the flesh of eggplant fruits. Consequently, red + blue LED irradiation can be considered as a convenient tool used for the postharvest of eggplant, with a positive effect in the increasing of important secondary metabolites. The obtained eggplant fruits proved to be a promising source of bioactive and antioxidant compounds for functional food production.

Effect of LED Lights on Secondary Metabolites and Antioxidant Activities in Red Pakchoi Baby Leaves

“…The findings were consistent with a previous study reporting that blue LED light increased the accumulation of anthocyanins and phenolic acids in Brassica juncea sprouts, and their extracts showed a higher antioxidant capacity . In addition, Jarerat et al reported that the peel of eggplant exposed to red + blue LED lights had the highest DPPH inhibition and ferric-reducing antioxidant power . As a result, for the accumulation of secondary metabolites (glucosinolates, flavonoids, and phenolic compounds) and antioxidant activity, plants exposed to a combination of red + blue LED light proved to be the most effective.…”

“… 51 In addition, Jarerat et al reported that the peel of eggplant exposed to red + blue LED lights had the highest DPPH inhibition and ferric-reducing antioxidant power. 52 As a result, for the accumulation of secondary metabolites (glucosinolates, flavonoids, and phenolic compounds) and antioxidant activity, plants exposed to a combination of red + blue LED light proved to be the most effective.…”

“…These findings were consistent with those from previous studies. Jarerat et al conducted the measurement of TPC and TFC contents accumulated in the peel and flesh of eggplants exposed to various types of LEDs (red, blue, and red + blue), indicating that mixed LED (red + blue) was found to be effective in the accumulation of total phenolics and total flavonoids in the flesh and peel of eggplants . Furthermore, Gam et al reported that mixed (blue + red) LEDs accumulated the highest total flavone content in Anoectochilus roxburghii compared to other light conditions (fluorescent lamp, blue-red, blue:red:white ratios of 1:5:1 and 1:4:2) …”

Short-term Anoxic Treatment of Litchi Fruit (<i>Litchi chinensis</i> Sonn. cv. Hong Huey) Delays Pericarp Browning and Maintains Physicochemical Quality During Storage

“…Total phenolic and flavonoid contents were analyzed according to the method of Jarerat et al (2022) with slight modifications. One gram of lyophilized pericarp was homogenized in 80% ethanol and centrifuged at 12,000 × g for 20 min at 4°C.…”

“…The Ferric Reducing Antioxidant Power (FRAP) assay was performed according to Jarerat et al (2022) with some modifications. Briefly, a fresh working solution was prepared by mixing 25 mL of 300 mM acetate buffer (3.1 g C 2 H 3 NaO 2 •3H 2 O and 16 mL C 2 H 4 O 2 ), pH 3.6, 2.5 mL of 10 mM TPTZ (2,4,6-tripyridyl-striazine) solution, and 2.5 mL of 20 mM FeCl 3 •6H 2 O, and then warmed at 37°C.…”