Isolation and structure elucidation of radical scavengers from Thymus vulgaris leaves.

2,2-Diphenyl-1-picrylhydrazyl radical (DPPH*) scavenging activity-guided fractionation of a leaf extract of Thymus vulgaris led to the isolation of the radical scavengers rosmarinic acid 1, eriodictyol, taxifolin, luteolin 7-glucuronide, p-cymene 2,3-diol, p-cymene 2,3-diol 6-6'-dimer, carvacrol, thymol, and a new compound, 2. The fractionation was considerably facilitated by using an on-line HPLC detector for radical scavenging activity. In this detector activity is monitored as the disappearance of the color of a postcolumn added stable radical after reacting with radical scavengers in a reaction coil.

Identification of radical scavengers in sweet grass (Hierochloe odorata).

Extracts from aerial parts of sweet grass (Hierochloe odorata) were active DPPH free radical scavengers. The active compounds were detected in extract fractions using HPLC with on-line radical scavenging detection. After multistep fractionation of the extract, two new natural products possessing radical scavenging activity were isolated, and their structures were elucidated by NMR and MS.

Total synthesis and bioactivity of some naturally occurring pterulones.

The naturally occurring pterulones 1, 3, and 13 were synthesized in high overall yield from readily available methyl 3-(2-propenyl)-4-(2-propenyloxy)benzoate (6) by employing ring-closing metathesis (RCM) as a key step. The biological activities of the synthesized pterulones were tested using cells of Rhodotorulaglutinis and Saccharomyces cerevisiae.