Effect of agricultural digestate on antioxidative properties and antimicrobial activity of hemp (Cannabis sativa) leaves.

The present study aimed to investigate the influence of the applied fertilizer (agricultural digestate) on antioxidative properties and antimicrobial activity of leaves of hemp 'Futura75' cultivar, valuable in the nutritional process. An attempt was also made to establish correlations between the antioxidative properties and antimicrobial activity of the leaves and fertilizer doses. The total polyphenol content (TPC) and free radical scavenging activity were determined by means of the spectrophotometric method, whereas the polyphenol profile was identified with the high-performance liquid chromatography (HPLC). Microbiological analyses were conducted using the following test strains: Staphylococcus aureus, Pseudomonas aeruginosa, Candida albicans, and Aspergillus niger. The highest contents of polyphenols and flavonoids and the highest DPPH radical scavenging activity were determined in the hemp leaves at the early growth phase (I harvest date) after digestate application in a dose of 30 L (i.e., 35.84 mg·GAE·g-1 DW, 59.30 mg QE·g-1 DW and 78.36mmol Trolox·kg-1, respectively). The applied digestate affected also the antimicrobial activity of hemp leaves when applied in doses of 30 L [18-37%] and 50 L [15-30%], causing a tangible increase in the growth inhibition zones of, particularly, Candida albicans in the leaves harvested in terms I, II and III.