Norlignan glucosides from Hypoxis hemerocallidea and their potential in vitro anti-inflammatory activity via inhibition of iNOS and NF-kB

Authors: ZULFIQAR, FAZILA - University Of Mississippi; KHAN, SHABANA - University Of Mississippi; ALI, ZULFIQAR - University Of Mississippi; WANG, YAN-HONG - University Of Mississippi; ROSS, SAMIR - University Of Mississippi; VILIJOEN, ALVARO - Tshwane University; KHAN, IKHLAS - University Of Mississippi

Submitted to: Journal of Natural Products
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/13/2020
Publication Date: 1/23/2020
Citation: Zulfiqar, F., Khan, S.I., Ali, Z., Wang, Y., Ross, S.A., Vilijoen, A.M., Khan, I.A. 2020. Norlignan glucosides from Hypoxis hemerocallidea and their potential in vitro anti-inflammatory activity via inhibition of iNOS and NF-kB. Journal of Natural Products. 172:112273. https://doi.org/10.1016/j.phytochem.2020.112273.
DOI: https://doi.org/10.1016/j.phytochem.2020.112273

Interpretive Summary: Hypoxis hemerocallidea, commonly known as African potato, is the most popular species among the genus used in African folk medicines in the form of powder, decoctions, infusions, tinctures, and extracts. A number of biological activities have been associated with this plant such as antioxidant, anti-inflammatory, antidiabetics, antidepression, antibacterial and anticancer. Phytochemical investigation of this medicinal plant was undertaken as part of our continuous efforts to explore chemical constituents of broadly consumed dietary/medicinal herbs that can serve as chemical and/or biological markers. As a result, nine new and ten known compounds were isolated from the crude extract of this plant. Anti-inflammatory activity and cytotoxicity of purified compounds and plant extract/ fractions were tested. Some of isolated compounds /plant extract or fractions showed anti-inflammatory activity but were not cytotoxic to a panel of cell lines included in the cytotoxicity assay.

Technical Abstract: Phytochemical investigation of the hydro-alcoholic extract of Hypoxis hemerocallidea corms resulted in purification and identification of 16 diarylpentanoid/norlignan glucosides (1-16) along with three other secondary metabolites (17-19). Out of them, nine norlignan glucosides hypoxhemerolosides A-I (1-9) were found to be new metabolites. Curcapicycloside (10) was isolated and identified for the first time in its original form, previously it was purified after methylation of the mixture and reported as a methylated derivative. Structure elucidation was mainly accomplished by Nuclear Magnetic Resonance (NMR) spectroscopic and mass spectrometric techniques. The anti-inflammatory activity H. hemerocallidea extracts (hydroalcoholic, ethyl acetate, and n-butanol soluble parts) and the isolated compounds were evaluated through inhibition of inducible Nitric Oxide Synthase (iNOS) and Nuclear Factor kappa-light-chain-enhancer of activated B cells (NF-kB). Compounds 3, 4, 5 and 13 and the ethyl acetate fraction inhibited nitric oxide production in Lipopolysaccharide (LPS)-induced macrophages.