Isolation, semi-synthesis, free-radicals scavenging, and advanced glycation end products formation inhibitory constituents from Parmotrema tinctorum

Abstract

Bioassay-guided separation of acetone extract from lichen Parmotrema tinctorum (Delise ex Nyl.) Hale led to the isolation of six major phenolic constituents (1–6). Compounds structures were established using NMR and mass spectral techniques. Further, to develop libraries on these scaffolds, a series of semi-synthetic derivatives were prepared (1a–1f, 2a–2b, 3a, 5a) and investigated for their free-radicals (2,2-diphenyl-1-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS)) scavenging and advanced glycation end products (AGEs) formation inhibitory activities. Amongst tested derivatives, 1a, 1d, 1e, 2a, and 5a showed strong ABTS scavenging potentials comparable to Trolox. In addition, these derivatives also manifested moderate AGEs formation inhibitory activities.

Keywords:

• AGEs inhibition
• antioxidant activity
• lichen substance
• Parmotrema tinctorum
• semi-synthetic derivatives

Acknowledgments

This research was performed as a part of the Indo-French LIA “Natural Products and Synthesis for Affordable Health” and acknowledgments are due to CSIR (India) and CNRS (France). Authors thank to Director, IICT for his constant encouragement and support.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

PPK & BS thank to CSIR for fellowship program and financial support.