Phenolic compounds from the lichen Parmotrema cristiferum (Taylor) Hale

Abstract

Introduction: Lichens are fungal and algal or cyanobacterial symbioses resulting in the production of specific metabolites with a great variety of effects such as antimycobacterial, antiviral, antiinflammatory, antipyretic and antiproliferative. Parmotrema cristiferum (Taylor) Hale, a species of foliose lichen, was collected at Champasack Province, Laos in April 2015. This paper describes the isolation and structure elucidation of nine compounds isolated from this lichen. Methods: Phytochemical investigations of the chloroform extract of the lichen P. cristiferum led to the isolation of nine pure compounds. Their chemical structures were elucidated by extensive HR-ESI-MS and 1D and 2D-NMR spectroscopic analysis, and comparison with previously published data. Results: From the studied lichen, nine compounds, orcinol (1), orsellinic acid (2), atranol (3), methyl beta - orsellinate (4), atranorin (5), diffractaic acid (6), lecanoric acid (7), bailesidone (8), and tinctorinone (9) were isolated, structurally elucidated and evaluated for their a-glucosidase inhibitory activity. Conclusions: Among isolated compounds, except 2, 4, and 7, the remaining six compounds were known for the first time from the lichen P. cristiferum. All these compounds were inactive in the a-glucosidase enzyme inhibitory assay.