A derivative of furan-2,3-diol from pandan extract

摘要

A pandan species, botanically named as Pandanus pygmaues (P. pygmaues) was studied. The chloroform extract of the leaves was fractionated. One pure compound 1̲ (5 mg) was obtained by using preparative Thin Layer Chromatography (TLC). It gave a purple spot after the TLC plate was sprayed with sulphuric acid (Rf = 0.61, hexane:acetone = 56ࢼ44). The molecular structure of 1̲ was later, determined by Nuclear Magnetic Resonance (NMR) experiments. The chemical shifts of the ¹³C-NMR spectrum (125 MHz, CDCl3) ranges from δC 29 °C 147 ppm. This showed the absence of a carbonyl group. In addition, two possible methoxy groups appeared at δC 55.99 and 54.20 ppm. Meanwhile, the ¹H-NMR spectrum (500 MHz, CDCl3) showed signals below δH 7.0 ppm only. Yet, it is believed that 1̲ could be an aromatic compound. Three aromatic protons appeared at δH 6.91 (s), 6.90 (d, J = 10 Hz) and 6.84 (dd, J = 8 Hz, 2 Hz). A broad singlet at δH 5.63 (br s) would correspond to a proton involving in a H-C-O- bond. Four aliphatic multiplets (δH 3 – 5 ppm) were also detected as a doublet at δH 4.75 (d, J = 4.2 Hz), two double doublets respectively at δH 4.26 (dd, J = 6.7, 9.5 Hz) and δH 3.89 (dd, J = 3.2, 9.5 Hz), and finally a multiplet at δH 3.12 (dd, J = 4.6, 6.7 Hz). The ¹H-NMR spectrum also displayed signals at δH 3.91 ppm, supporting the hypothesis for the methoxy groups. It is suggested that respectively one dimethoxyphenyl and oxygenated five-membered ring could be constructed for compound 1̲. This finding could be considered unusual, in comparison to the common occurrence of pyrrolidinyl-α,β-unsaturated-γ-lactones from pandan extracts. In summary, --it is concluded that 1̲ could possibly be a tetrahydro-5-(2,4-dimethoxyphenyl)furan-2,3-diol.