Pharmacological activities of corn cobs xylan

Xylan is the second most abundant polysaccharide on Earth, surpassed only by cellulose. Among annual agricultural residues, corn cobs are a plentiful and renewable reservoir of xylan with a content of up to 40%. With the current U.S. corn production, 40 million metric tons of corn cobs on average are annually available for harvest. While many studies have investigated the physico-chemical properties, little research has been performed on the biological activities of corn cob xylan. The objective of this study was to evaluate the biomedical potential of xylan extracted from corn cobs grown in South Dakota, USA. Methods were developed to isolate, characterize and test corn cob xylan for its antioxidant, antibacterial and antitumor activities.  Extraction with dimethyl sulfoxide (DMSO) and NaOH was preceded by delignification of corn cobs to yield xylan of altering purities, composition, and molecular weights. Delignified corn cobs extracted with DMSO produced a xylan polymer that had superior characteristics over the other xylan extracts tested. The free radical scavenging capabilities of this xylan, determined against 2,2-diphenyl-1-picrylhydrazyl (DPPH), was in excess of 80% oxidative activity reduction. In addition, the antitumor tests conducted with human breast cancer cells (cell line MCF7) showed encouraging results in excess of 60% tumor cell death. These studies suggested apoptosis through enhanced mitochondrial production of reactive oxygenated species and inhibited G1 cell cycle arrest. The significance of the biological activities of corn cob xylan will be discussed.