Discovery of Natural Phosphodiesterase 5 Inhibitors from Dalbergia cochinchinensis Pierre Leaves Using LC-QTOF-MS2

The imbalance of phosphodiesterase 5 (PDE5) enzyme in the male body, or excessive PDE5 enzyme levels, can occur due to factors such as aging, diseases (e.g., cardiovascular disease, diabetes, depressive disorder), and physical behaviors (e.g., alcoholism, smoking, stress). PDE5 is directly associated with erectile dysfunction disease. Currently, many studies aim to find natural PDE5 inhibitors as an alternative to commercial drugs. This study is the first to demonstrate that the ethanolic leaf extract of <i>D. cochinchinensis</i> exhibits potent PDE5-inhibitory activity. The PDE5-inhibitory activity of five plant parts was evaluated: leaf (IC₅₀ = 1.53 ± 0.12 µg/mL), twig (3.37 ± 0.54), fruit (14.92 ± 2.85), heartwood (19.05 ± 5.60), and bark (16.03 ± 2.92). However, there is still uncertainty about which compounds in leaf extract are responsible for the PDE5 inhibition. Therefore, the purpose of this study is to identify the chemical constituents in the leaf of <i>D. cochinchinensis</i>, including determining which of these compounds may act as PDE5 inhibitors. This study was achieved using at-line LC-QTOF-MS².