Pandanus amaryllifolius Exhibits In Vitro Anti-Amyloidogenic Activity and Promotes Neuroprotective Effects in Amyloid-ß-Induced SH-SY5Y Cells.

Accumulation of amyloid-beta (Aß) plaques leading to oxidative stress, mitochondrial damage, and cell death is one of the most accepted pathological hallmarks of Alzheimer's disease (AD). Pandanus amaryllifolius, commonly recognized as fragrant screw pine due to its characteristic smell, is widely distributed in Southeast Asia and is consumed as a food flavor. In search for potential anti-AD agents from terrestrial sources, P. amaryllifolius was explored for its in vitro anti-amyloidogenic and neuroprotective effects. Thioflavin T (ThT) assay and the high-throughput screening multimer detection system (MDS-HTS) assay were used to evaluate the extracts' potential to inhibit Aß aggregations and oligomerizations, respectively. The crude alcoholic extract (CAE, 50 µg/mL) and crude base extract (CBE, 50 µg/mL) obstructed the Aß aggregation. Interestingly, results revealed that only CBE inhibited the Aß nucleation at 100 µg/mL. Both CAE and CBE also restored the cell viability, reduced the level of reactive oxygen species, and reversed the mitochondrial dysfunctions at 10 and 20 µg/mL extract concentrations in Aß-insulted SY-SY5Y cells. In addition, the unprecedented isolation of nicotinamide from P. amaryllifolius CBE is a remarkable discovery as one of its potential bioactive constituents against AD. Hence, our results provided new insights into the promising potential of P. amaryllifolius extracts against AD and further exploration of other prospective bioactive constituents.

p-Coumaroyl Malate Derivatives of the Pandanus amaryllifolius Leaf and Their Isomerization.

A novel p-coumaroyl dimethyl malate (1) was isolated from the Pandanus amaryllifolius leaf in addition to three known analogs of p-coumaroyl dimethyl malate (2-4), and their structures were elucidated by analysis of the spectroscopic data. The p-coumaroyl malate derivatives were isolated as a mixture of E and Z isomers. To determine the cause of isomerization, the p-coumaroyl malate isolated in this study was synthesized. We concluded that the Z isomer might be an artifact generated from the E isomer through purification steps.