Acúmulo de saponinas bioativas em Quillaja brasiliensis induzido por irradiação Ultravioleta-C e luz vermelha no período póscolheita

Abstract

Saponins are terpene metabolites found in several plant species. A fraction of triterpene saponins from leaves of Q uillaja brasiliensis, named QB90, has shown great potential as immunoadjuvant in vaccines, constituting a sustainable source of metabolites with this useful bioactivity. It has been shown that higher concentrations of these saponins can accumulate in detached leaves of young plants by exposure to red light or UVC irradiation. These studies have used frames with cellophane filters to filter the fluorescent light output and enrich for red light irradiance reaching leaves. The present study aimed at evaluating if LED lamps can be viable alternatives to cellophane filters as sources of red irradiance for treating detached leaves to increase QB90 concentration, as well as to examine the effect of combined exposure of UVC and red light on bioactive saponin yield. The source of leaves for the present experiments was 11 monthold seedlings of Q . brasiliensis , cultivated under controlled conditions. Both red light enrichment methods, LED lamps or cellophane filter, had the same stimulatory effect on QB90 accumulation. The combined treatment of 15 minutes of UVC followed by 11 h and 45 min of red light irradiance promoted QB90 accumulation, but did not show significant differences when compared to 12 hours of red light treatment or 15 minutes of UVC followed by 11 hours and 45 min of white light irradiation treatment. The treatment combining red light with 3 UVC pulses yielded no increase of the QB90 concentration in comparison to the control. Therefore, red light, provided by LEDs, or UVC exposure for 15 min are the best choices of postharvest treatment to increase QB90 concentration in leaves.