Undescribed C-Glycosylflavones from corn silk and potential anti-inflammatory activity evaluation of isolates

Authors: SARFARE, SATISH - Sies College Of Arts, Science & Commerce Sies College Of Arts; KHAN, SHABANA - University Of Mississippi; ZULFIQAR, FAZILA - University Of Mississippi; RADHAKRISHNAN, SRIVEDAVYASASRI - University Of Mississippi; ALI, ZULFIQAR - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi

Submitted to: Planta Medica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/23/2021
Publication Date: 3/3/2022
Citation: Sarfare, S., Khan, S.I., Zulfiqar, F., Radhakrishnan, S., Ali, Z., Khan, I.A. 2022. Undescribed C-Glycosylflavones from corn silk and potential anti-inflammatory activity evaluation of isolates. Planta Medica. https://doi.org/10.1055/a-1728-1347.
DOI: https://doi.org/10.1055/a-1728-1347

Interpretive Summary: Corn silk (Stigma maydis) is a waste product from corn (Zea mays L., Poaceae/Gramineae) cultivation. Corn silk is a thread-like silky material found between an ear of corn and an outer husk that expands from the female flower of the corn and changes color from light green to red/yellow/golden and brown. Corn silk has been used as traditional medicine as an effective herbal remedy for prostate, urinary tract infections, malaria, and heart issues. Some recent pharmacological studies have shown the effectiveness of corn silk against hyperglycemia, obesity, cardiovascular and neurological disorders, cystitis, prostatitis, edema, nephritis, gout, urinary infections, inflammation, oxidative stress, and bacterial infections. Most of these biological activities are associated with the flavonoid contents particularly C-glycosidic flavonoids which are abundant in corn silk. Nearly 29 flavonoids including about ten C-glycosylflavones have been reported from corn silk. Phytochemical investigation of the corn silk was done as part of a program to isolate the chemical metabolites which could be used as chemical/biological markers. As a result, four C-glycosylflavones, a triterpenoid, and four sterols were isolated and characterized. The isolated compounds were subjected to a series of bioassays for anti-inflammatory activity that determine the inhibition of intracellular nitric oxide generation and reactive species generation in response to inflammatory stimuli and the activation of nonsteroidal anti-inflammatory drug activated gene-1 (NAG-1) in selected cell lines.

Technical Abstract: Phytochemical investigation of corn silk resulted in isolation and characterization of four flavone C-glycosides, chrysoeriol 6-C-ß-oliopyranosyl-7-O-ß-D-glucopyranoside (1), 3'-methoxycassiaoccidentalin A (2), chrysoeriol 6-C-ß-boivinopyranosyl-7-O-ß-D-glucopyranoside (3), and ax-4"-OH-3'-methoxymaysin (4), a triterpenoid, friedelin (5), and four sterols, (22E)-5a,8a,-epidioxyergosta-6,22-dien-3ß-ol (6), 6ß-hydroxystigmasta-4,22-diene-3-one (7), ß-sitosterol, and stigmasterol. Compounds 1 and 2 were previously undescribed. Structure elucidation of the isolated compounds was attained using spectral data including 1D and 2D NMR and HRESIMS. Compounds 1, 2, 5, and 7 inhibited iNOS activity in macrophages with IC50 values of 25, 23, 9, and 19 µM, respectively. Compounds 1 and 2 also induced NAG-1 activity about two fold in chondrocytes. The extract of cron silk, however, did not exhibit inhibition of iNOS or NF-kB but induced NAG-1 about two fold.