Characterization of hemp (Cannabis sativa L.) raw bast fibers of monoecious versus dioecious cultivars from flowering to senescence: FTIR of lignocelluloses and extract bioactivities

Hemp is a multipurpose crop. Due to the revived interest in sustainable crops, hemp cultivation has increased in recent years. Both dioecious and monoecious hemp varieties are cultivated, yet few studies provide a comparative characterization. Monoecious cannabis plants are more uniform and economically efficient, being a whole-plant harvesting type. The aim of this research was to provide a comparative characterization of monoecious versus dioecious hemp bast fibers. There was conducted a microscopic analysis that showed their localization, the FTIR characterization of raw lignocellulosic fibers and extract bioactivity assays (antioxidant and microbiologic). Results indicated that FTIR absorbance ratios of peaks 1427/897 cm^-1, 1373-1375/667 cm^-1, and1373/2905-2910 cm^-1 are relevant for hemp fibers parameters. A significant positive correlation was found between total phenolic content and antioxidant activity (r = 0.69*, r = 0.56*). Analysis of raw bast fibers extract indicated that the monoecious cultivar in the senescence phenophases had highest total phenolic content, and was more effective against all tested pathogenic bacterial strains. Both monoecious cultivar and male plants of the dioecious cultivar had higher total phenolic content than female plants of the dioecious cultivar, although at different phenophases. The male plants in the technological maturity phenophases presented the highest total phenolic content. Lower antioxidant activity was registered by female plants of the dioecious cultivar, which also showed lower total phenolic content, and the extract had no effect against Listeria monocytogenes, regardless of harvest time. The findings thus point to monoecious cultivars as having potential relevance in applications requiring enhanced bioactive properties, besides being advantageous for large-scale cultivation for fibers and seeds due to the economic efficiency.