Free Radical Scavenging Activity of Non Saponifiable Lipids from Dieffenbachia picta (Lodd.) Schott. Leaves and Identification of a Lanostane Triterpenoid

Abstract

Dieffenbachia picta (Lodd.) Schott, mostly used as ornamental plant, has not been thoroughly investigated for its medicinal properties due largely to the presence of oxalic acid deposited as crystals of calcium oxalate on parts of the plant especially the leaves. The present study however was aimed at providing an in-vitro evidence for the potential radical inhibitory activity of isolates obtained from n - hexane fraction of D. picta leaf found to have antioxidant properties in our previous study. Isolation of compounds was achieved by gradient elution column chromatographic technique. Ultra Violet/visible (UV), Infrared (IR) and Nuclear Magnetic Resonance (NMR-1D and 2D) spectroscopic techniques were used for structural elucidation. Molecular mass was ascertained by low and high resolution Electron Impact (EI/EI-HR) mass spectrometry. Gas chromatography (GC) and gas – chromatography mass spectrometry (GC-MS) were used to characterize the lipid component.  Free radical scavenging activity of the isolates was assessed using 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method and butylated hydroxylanisole (BHA) was used as standard. Structures were proposed for the non saponifiable lipids as Tetradecyloctadecyl behenate (DP1) and 1~chlorotritriacontane (DP2) while phytol (31.44%), isopropyl palmitate (14.91%), isopropyl stearate (8.61%) were the major constituents of the oil (DP3). A lanostane triterpenoid 11β, 19-epoxy-Lanostan-3β-ol was also identified in the oil. DP1 and DP3 exhibited significant antioxidant activity with IC₅₀ (μM) values of 43.5± 0.53 and 25.43±0.06 respectively comparable to the standard. The results of the present study indicated that D. picta is rich in antioxidant metabolites despite the presence of toxic calcium oxalate crystals.

Keywords: Tetradecyloctadecyl behenate; phytol; 11β, 19-epoxy-Lanostan-3β-ol; 2, 2-diphenyl-1-picrylhydrazyl radical; Dieffenbachia picta