Investigation of appropriate phenolic compound extraction methods for Sorghum bicolor (L.) Moench shoot extracts from different cultivars

This study was conducted to examine total phenolic contents of Sorghum bicolor (L.) Moench shoot extracts in different cultivars andunder different extraction methods by HPLC analysis. In the first experiment, five cultivars of sorghum (Milyang-1ho, Milyang-5ho, Donganme, Hwanggumchal and Nampungchal) were extracted by soaking in distilled water for 24h at room temperature and boiling for 2 h, followed by filtering and evaporating. For the second experiment, focus was given to a known allelochemical, the phenolic compound 4-hydroxybenzoic acid. Hwanggumchal, the cultivar with the highest 4-hydroxybenzoic acid content from the first experiment, was chosen for optimizing phenolic compound extraction under different conditions such as solvent (distilled water or ethanol), temperature (4o, 25o and 40°C), and time (24, 48 and 72 h). An HPLC system was used to quantitatively determine total phenolic contents of extracts. Results showed that, between the five cultivars, Donganme had the highest total phenolic compounds (402.6 mg/l), while Hwanggumchal had the highest amount of 4-hydroxybenzoic acid (96.0 mg/l). In the second experiment, the highest amount of total phenolic compounds was obtained when the sorghum samples were extracted in ethanol by soaking for 72 h at 40°C, while the lowest amount was obtained by soaking 72 h at 4°C in distilled water. The study and application of the allelopathy phenomenon in weed control is essential for the protection of the environment. If adopted successfully, it could lead to significant accomplishments for sustainable agriculture.