An unusual diterpene glycoside from the nuts of almond (Prunus amygdalus Batsch)

A new unusual kauranoid diterpene glycoside, named amygdaloside, was isolated from the nuts of almond (Prunus amygdalus). It’s structure was established as 17-O-D-glucopyranoside ent-6,7-epoxy-6-hydroxyl-6,7-secokaur-19-oic acid, 6,19lactone 16 17-diol on the basis of high-resolution 1D and 2D NMR spectral studies. © 2003 Elsevier Science Ltd. All rights reserved. Nutraceuticals are naturally-derived, bioactive (usually phytochemical) compounds that have health promoting, disease preventing or medicinal properties. Nutraceutical compounds or substances can be delivered in the form of food (functional food) or as a dietary supplement, or in both forms. In recent years, both the agri-food industry and individual consumers have looked to food not only for basic nutrition, but also for health benefits. These considerations prompted us to undertake systematic studies on the bioactive constituents of almonds (Prunus amygdalus Batsch), which belong to the Rosaceae family that also includes apples, pears, prunes, and raspberries. Almonds are one of the most popular tree nuts on a worldwide basis and rank number one in tree nut production. They are typically used as snack foods and as ingredients in a variety of processed foods, especially bakery and confectionery products. The United States is the largest almond producer in the world. In this report, we describe the isolation and structural elucidation of amygdaloside, which has an unusual B ring-cleaved kauranoid skeleton (1) from the nuts of almond. The ethanol extract of almond nuts was chromatographed successively on silica gel and RP C-18 columns to afford compound 1 (35 mg). It’s structure was established by assignments of 1D and 2D NMR spectra supported by MS data. Compound 1 has the molecular formula C26H40O10, established by positive-ion HRFAB-MS (m/z 513.2688, [M+H]; calcd for C26H41O10: 513.2699) as well as C and DEPT NMR spectral data (Table 1). It’s IR spectrum displayed characteristic absorptions for hydroxyl groups (3400–3500 cm), a glycosidic linkage (1000– 1100 cm), and a five-membered lactone (1759 cm). A total of 26 carbon signals were observed in the C NMR spectrum, six of which could be assigned to the terminal glucopyranoside. The identification of 1 as a diterpenoid derivative was supported by the remaining carbon resonances and associated DEPT signals: two methyl groups ( C 17.9 and 27.8), nine methylene groups ( C 15.7, 19.1, 23.7, 26.1, 31.3, 37.4, 50.4, 75.1 and 75.2), two of which carried oxygen atoms ( C 75.1 and 75.2), four methine groups ( C 45.8, 50.5, 57.6 and 103.6), one of which was a hemiacetal functionality ( C 103.6), four quaternary carbons ( C 38.7, 44.3, 50.5 and 81.0) including one oxygenated carbon ( C 81.0), and one ester carbonyl carbon ( C 179.4). This hypothesis was confirmed by the H NMR spectrum of 1, which showed two tertiary methyl groups at H 1.03 (s) and