The chemical composition and antioxidant activity of essential oils and extracts of Dalbergia odorifera leaves

To analyze the chemical composition and evaluate the potential commercial value of Dalbergia odorifera leaves, the chemical component and content of the essential oils (EOs), fatty acids (FAs), polyphenols and flavonoids in the leaves of D. odorifera were studied. The composition of the EOs obtained by simultaneous distillation extraction (SDE) (at the yield of 0.092%) and hydro-distillation (HD) (at the yield of 0.050%) from D. odorifera leaves was analyzed by gas chromatography-mass spectrometry (GC-MS). Seventy-six compounds were identified and the major compounds were phytol (22.5–24.3%), 4-vinylguaiacol (8.7–12.7%), dihydroedulan II (7.4–11.2%), γ-elemene (5.1–6.2%), cedrol (2.8–6.1%), coumaran (0.9–3.1%) and hexahydrofarnesyl acetone (2.5–2.7%). The FA yield extracted by ultrasound was 1.145% (w/w), and the most abundant FA components were palmitic acid (C16:0), oleic acid (C18:1) and linoleic acid (C18:2) in leaves. The results of the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and 2,2′-azino-bis (3-ethylbenzothiazoli-ne-6-sulfonic acid (ABTS+) radical scavenging experiments demonstrated that the EOs and FAs possess strong antioxidant activity. The ethanol extract of the leaves had a high polyphenol content [16.00 mg gallic acid equivalent (GAE) g−1 dry weight (DW)] and flavonoid content [8.92 mg rutin equivalent (RE) g−1 DW]. This research has determined qualitatively and quantitatively the isoflavonoids (biochanin A, isoliquiritigenin, tectorigenin and genistein) by ultra-performance liquid chromatography-electrospray ionization-tandem mass spectrometry (UPLC-ESI-MS/MS). The phytochemical analysis (EOs, FAs and flavonoids) of the extract showed that the D. odorifera leaf is a rich source of high bioactive compounds and might have the potential to be recommended for further cosmetics, food and pharmaceutical applications.