Stilbenes

A narrow distribution — grapes, knotweed, peanuts, pines and a few others:

Almost every resveratrol supplement on the market is knotweed extract, not grape — the grape connection is marketing lineage rather than sourcing.

Resveratrol became the most-hyped plant compound of the 2000s on the strength of the French paradox and reports that it activated the longevity protein SIRT1 and extended lifespan in yeast and worms. Much of that has not held up: the SIRT1 activation was substantially an artefact of the fluorophore-based assay used, and the lifespan findings did not replicate consistently in mammals.

The bioavailability picture is worse still. Oral resveratrol is absorbed reasonably but conjugated so fast that free plasma levels sit far below the concentrations used in the cell-culture work everything was built on. Human trials have been mostly small and mixed.

This is not a reason to dismiss the class — pterostilbene, the dimethylated relative, is meaningfully more bioavailable and holds a more defensible position — but it is the clearest example on this site of preclinical excitement outrunning human evidence, and worth carrying as a general caution.

The reproducible effects are anti-inflammatory and metabolic, and modest. Resveratrol shows small improvements in insulin sensitivity and endothelial function in some trials, and it is a genuine antioxidant and mild oestrogen-receptor ligand.

Pinosylvin and the other pine stilbenes retain real antifungal activity — the phytoalexin function the class evolved for.