Chemical Constituents of Lonicera maackii

Abstract

Lonicera maackii (Rupr.) Maxim. (Amur honeysuckle in English, gold and silver wood in Chinese) is a kind of deciduous shrub belonging to the family of Caprifoliaceae and is native to temperate Asia in northern and western China, Mongolia, Japan, Korean, and Southeast of Russian. In China, Lonicera maackii is widely planted at the street side and in public gardens to beautify the environment and for sightseeing because of its fragrant flowers, long flowering period, and attractive red fruits; the fruits are usually eaten by birds but is toxic to humans. Chen Yue-kai [1] has studied the total flavonoid content in the flowers, branches, leaves, and fruits of Lonicera maackii. We have studied the volatile constituents by GC-MS [2] and isolated seven compounds [3] from the fruits of L. maackii planted in Ningxia Province, China. Based on these studies, we continue to study this plant to find new structural compounds. In this work, chlorogenic acid (CA, 1) was isolated from the flower, and six known triterpene compounds (2–7) were isolated for the first time from the fruits of Lonicera maackii. NMR spectra were recorded on a Bruker Biospin Avance III spectrometer. Column chromatography (CC) was carried out on silica gel (100–200 or 200–300 mesh, Qingdao Marine Chemical Inc., Qingdao, China). Melting points were determined on an X-4 apparatus equipped with a microscope and are uncorrected. Plant Material. The flower was collected from the campus of Ningxia Medical University (Ningxia Province, China) in April of 2010 and air dried naturally. The fruits of Lonicera maackii were collected from the campus of Ningxia Medical University in October of 2010 and air dried naturally. Extraction and Isolation. The dry powdered flower of Lonicera maackii (50 g) was extracted by ultrasonic wave with 95% ethanol for three times. The combined extract was concentrated under reduced pressure. The residue was rechromatographed over a column of silica gel with chloroform–methanol (10:1 to 1:1) eluent to obtain chlorogenic acid (1). The air-dried and powdered fruits (1 kg) of Lonicera maackii were dipped in 2 L chloroform for one month and then filtered; the filtrate was concentrated, and the residue was rechromatographed directly over a column of silica gel with eluents of petroleum ether, petroleum ether–ethyl acetate (5:1 to 1:1), pertroleum ether–acetone, ethyl acetate, and chloroform–methanol (10:1 to 1:1) to obtain several fractions. The fractions were isolated by preparative thin-layer chromatography (PTLC) to obtain six known triterpene compounds (2–7).