Suggesting a derivative of isoindol-1-one from a Vitex species

A light yellow amorphous solid (compound A̲, 760 mg) was isolated from a silica column chromatography of the crude methanolic leaves extract of Vitex trifolia. It gave a thin layer chromatographic spot (TLC; Rf = 0.80 in chloroform: methanol = 80∶20). Compound ̲ was visible under short UV light and appeared orange under long UV light. Here, the chemical structure for ̲ is proposed. In agreement with the preliminary Nuclear Magnetic Resonance spectrum (¹H-NMR, 500 MHz, CDCl3, δH 3 – 12 ppm) and those reported in the literature, the main skeleton for this constituent might be a nitrogenous aromatic compound. The signal at δH 3.91 ppm indicates that ̲ carries a methoxy group. Meanwhile, the signals at δH 5.18 and δH 5.95 ppm shows the possibility of ̲ containing a hydroxyl and a phenolic group. Another two phenolic protons respectively resonate at δH 7.30 and δH 7.81 ppm. A peak at δH 8.20 ppm would correspond to a proton of a secondary amine. Next, the peak at δH 11.37 ppm could be assigned either to an aldehyde group or to a phenolic having the intramolecular hydrogen bonding with a keto group at its β-position. It is suggested that ̲ could be a derivative of isoindol-1-one. This finding would enhance the library of Vitex phytochemicals, in addition to its antioxidative phenylnaphthalene-type lignan alkaloid and cytotoxic labdane-type diterpenoids.