Prenylated flavonoids are an important class of naturally occurring flavonoids with important biological activity, but their low abundance in nature limits their application in medicines. Here, we showed the hemisynthesis and the determination of various biological activities of seven prenylated flavonoids, named 7–13, with an emphasis on antimicrobial ones. Compounds 9, 11, and 12 showed inhibitory activity against human pathogenic fungi. Compounds 11, 12 (flavanones) and 13 (isoflavone) were the most active against clinical isolated Staphylococcus aureus MRSA, showing that structural requirements as prenylation at position C-6 or C-8 and OH at positions C-5, 7, and 4′ are key to the antibacterial activity. The combination of 11 or 12 with commercial antibiotics synergistically enhanced the antibacterial activity of vancomycin, ciprofloxacin, and methicillin in a factor of 10 to 100 times against drug-resistant bacteria. Compound 11 combined with ciprofloxacin was able to decrease the levels of ROS generated by ciprofloxacin. According to docking results of S enantiomer of 11 with ATP-binding cassette transporter showed the most favorable binding energy; however, more studies are needed to support this result.

To evaluate the in vitro and in vivo antifungal capability of diverse compost teas of endemic Chilean flora inoculated with a consortium of fungal strains of Trichoderma spp. (biocontrol agent) against three important phytopathogens: Botrytis cinerea, Fusarium oxysporum and Lasiodiplodia theobromae. Compost teas were obtained from endemic flora of Chile (Azara celastrina, Citronella mucronate, Cryptocarya alba, Peumus boldus and Quillaja saponaria). Eleven Trichoderma strains were isolated and antagonism tests were performed to develop fungal consortia with biocontrol properties. The biocontrol effect of compost teas inoculated with Trichoderma consortia was also analyzed. The results showed that the teas possess antifungal activity against B. cinerea and F. oxysporum and, to a lower degree against L. theobromae. In vitro tests showed that Trichoderma consortia improved the suppressive effect against B. cinerea (94%–97%), F. oxysporum (89%–92%) and L. theobromae (51%–73%). P. boldus tea showed the highest suppressive effect against the plant pathogen L. theobromae. In addition, the in vivo assay showed that tomato plants treated only with Trichoderma or compost tea, did not show differences in height with regard to control plants. However, when these two treatments were combined, the best performance in plant height and protection against pathogens was observed. This study indicates that the addition of a consortium of Trichoderma strains with intra- and interspecific incompatibilities, significantly improves the inhibitory effect of compost teas in in vitro tests against the plant pathogenic fungi, while in vivo, enhances tomato plant growth and reduce plant disease symptoms.