Natural variability and antioxidant properties of commercially cultivated switchgrass extractives

Optimum utilization of lignocellulosic bioenergy feedstock, such as switchgrass, via recovery of value-added phytochemicals and reduction of waste streams will increase the economic feasibility as well as the sustainability of integrated biorefineries. Switchgrass contains significant amount of overlooked non-structural components, i.e. extractives, which encompasses phenolic derivatives with potential antimicrobial and antioxidant properties. As a perennial crop, it is essential to assess the natural variability of switchgrass extractives content and composition in order to determine the feasibility of its extraction and utilization. In this study, three switchgrass cultivars were harvested from four commercial farms in their second and third growing seasons. Their respective extractive fractions were characterized for the presence of free sugars, total phenolics (TPC), hydroxycinnamic acid (HCAs) derivatives, total flavonols, and other important phytochemicals. Biomass harvested in the third growing season displayed greater amounts of TPC, HCAs, and total flavonols. Environmental conditions such as total precipitation, and cultural practices including harvest time, played important roles in the accumulation of TPC. The switchgrass extractives also exhibited DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging activity with a positive correlation between inhibiting concentration (IC₅₀) value and total flavonols content.