Constituents of and their anti-amyloidogenic activity.

The aggregation of amyloid-β (Aβ) remains the most acceptable pathological hallmark of Alzheimer's disease (AD). In search for natural products exhibiting anti-amyloidogenic effects, phytochemical analyses were conducted on leading to the purification of oxindole alkaloid uncarine E (isopteropodine) (), the phenylethanoid tyrosol (), the megastigmane vomifoliol (), and the previously reported alkaloids mitraphylline and isomitraphylline. This is the first report of compounds - in the title plant, and tyrosol () from the genus . Assessment of the anti-amyloidogenic potential using Thioflavin T assay showed 91% (at 50 µM) and 70% (at 25 µM) inhibitions for compound . Tyrosol () gave 76% (at 50 µM) and 63% (at 25 µM) inhibitions. These compounds may be further tested to elucidate their mechanism in the prevention of Aβ aggregation. To the best of our knowledge, this is the first report on the anti-amyloid aggregation activity of compounds and .