Agrobacterium-elicited Hypericum perforatum cell methanolic extract shows antibacterial activity against human pathogens

Hypericum perforatum (HP), an important medicinal plant that possesses several pharmacological properties, remains recalcitrant to Agrobacterium tumefaciens (AT) mediated transformation. Upon co-cultivation, AT viability was reduced completely HP cells defense response [1]. Further, we reported that the antibacterial and antioxidant activities of HP cells were increased several fold after elicitation with AT that provide antimicrobial and antioxidant protection to HP cells [2]. Recently, our group has demonstrated that the AT- elicited HP extract render protection against oxidative stress induced in human HepG2 cells [3]. Here, we report that the antibacterial activity of methanolic extract of HP cells elicited with AT against important human bacterial pathogens (Staphylococcus aureus and Bacillus subtilis). Briefly, equivalent concentration of methanolic extract of elicited and control HP cells were added to overnight cultures of S. aureus and B. subtilis. After 24h of incubation, the bacterial cultures were serially diluted and spread on LB plates. Colony forming units were counted after 2 – 3 days of incubation of plates at 37 ° C. Among various dilutions checked, 10 – 6 dilution exhibited countable number of colonies in cultures without any treatment (control) and un-elicited HP extract treatment. Whereas, countable number of colonies in elicited extract treatments was only found in 10 – 1 dilution revealing that the antibacterial activity of elicited HP cell extract against these pathogens is 105 times higher than un-elicited extract. Our results reveal that the increase in antimicrobial activity in AT elicited HP cells is not restricted to AT, a phytopathogen, but also extends to human pathogens. Testing of several other human bacterial pathogens, resistant to antibiotics is ongoing in our lab