Cannabis sativa L. is well known for its secondary metabolites such as cannabinoids, terpenes and phenolic compounds [1]. However, despite being one of the oldest cultivated crops, hemp remains highly controversial due to its psychoactive properties, and research on it is still lacking. Although data on Cannabis sativa L. inflorescences, leaves and stems are increasing, the roots remain an extremely understudied part of the plant. Hemp roots have been used in medicine since the beginning of our era. They were mostly used to treat fever, gout, arthritis, joint pain and inflammation [2]. However, only from 0.001 to 0.004% of cannabinoids are found in the roots, so research on them is not so relevant, as most of today's scientists focus mainly on the cannabinoids. Nevertheless, looking at the history of hemp roots use, it is worth investigating their chemical composition and biological activity [3]. Therefore, the goal of this study was to evaluate the influence of sowing density on the chemical composition and antioxidant activity of Cannabis sativa L. roots.
The experiment was conducted in 2022 at the experimental base at Lithuanian Research Center for Agriculture and Forestry located in Central Lithuania (55°24′ N, 23° 52′ E, 65 m asl) on an Endogleyic Endo- stagnic Endocalcaric Luvisol (Loamic) soil according to WBR [4]. Industrial hemp variety Felina32 (French national hemp grower association) was sown in two densities (15 and 35 kg ha-1). Harvest was carried out manually at full maturity on the 19th of September. Dried hemp roots were ground using a coffee beans mill. 1 g of Cannabis sativa L. roots flour was extracted with 10 mL 70% methanol solution and placed into an ultrasonic bath at room temperature for 1 hour. Extracts were filtered through a 45 μm nylon filter and kept at 4°C until analysis. The extracts were used to determine total polyphenolic compounds (TPC), total flavonoids (TFC), total polyphenolic acid (TPA) content and antioxidant activity by DHHP assays.
The results revealed that higher sowing density decreased biologically active compounds in hemp roots. Increasing the density from 15 to 35 kg ha-1 the total amount of polyphenolic compounds decreases by approximately 2.42 times (from 10.77 ± 1.36 to 4.45 ± 0.98 mgRUE g-1 DW), total flavonoid content about 6.65 times (from 14.51 ± 0.75 to 2.18 ± 0.13 mgRUE g-1 DW) and total polyphenolic acid content decreases from 9.49 ± 0.54 to 0.96 ± 0.33 mgCAE g-1 DW it is almost 10 times. Accordingly, the antioxidant activity also decreased.
In conclusion, the performed research shows that lower sowing density has a positive effect on the chemical composition of hemp roots as they can accumulate larger amounts of biologically active substances.