LAUSR

White pepper (Piper nigrum L.) and long pepper (Piper longum L.), distributed mainly in tropical regions, belong to the genus Piper L., including approximately 2000 species, of which about 60 species are found in China [1]. Piper nigrum L. and Piper longum L. have long been regarded as the most significant couplet medicines, which are widely used to treat acute or persistent diarrhea and stroke in traditional Chinese Hui medicine [2, 3]. Recent pharmacological studies have indicated that the couplet medicines have obvious antimicrobial, anti-inflammatory, antiplatelet aggregation, anti-atherogenic, antifibrosis, and hypolipidemic activity [4–8]. Previously, chemical compounds have been isolated and identified from white pepper and long pepper, including alkaloids, phenolics, terpenes and essential oils [9–11]. Here, we describe the isolation and structural identification of 21 compounds (1–21) and evaluate the effect of 10 compounds from white pepper and long pepper on the oxygen glucose deprivation (OGD) model. Compounds 12–18, 20, and 21 were isolated for the first time from the genus Piper L. From a 70% ethanol extract of the fruits of white pepper and long pepper, 21 compounds (1–21) were obtained. Their structures were characterized as piperine (1) [12], piperanine (2) [13], piperolein A (3) [14], piperolein B (4) [15], (4E)-5-(1,3-benzodioxol-5-yl)-1-(1-piperidinyl)-4-penten-1-one (5) [14], pipernonaline (6) [13], guineensine (7) [16], pipercide (8) [17], dihydropiperlonguminine (9) [18], pipercyclobutanamide A (10) [19], hinokinin (11) [20], pipercyclobutanamide G (12) [21], pipercyclobutanamide H (13) [21], pipercyclobutanamide C (14) [19], (2S,3S)-2-(5-methoxy-3,4-methylenedioxybenzyl)3-(3,4-methylenedioxybenzyl)butyrolactone (15) [22], 4-hexyl-4,6-dimethyl-4,5-dihydropyrrolo[1,2-a]quinoxaline (16) [23], N-(5,6,7,8-tetrahydronaphthalen-2-yl)acetamide (17) [24], ent-4(15)-eudesmene-1β,6α-diol (18) [25], 3-(3′,4′-methylenedioxophenyl)propenal (19) [26], 7-demethoxyegonol-9(Z),12(Z) linoleate (20) [27], and dibutyl phthalate (21) [27]. General Comments. Column chromatography was carried out on Sephadex LH-20 gel (25–100 μm, General Electric Company), ODS-A-HG (50 μm, YMC Co., Ltd), and silica gel column (100–200 mesh, Qingdao Marine Chemical Factory, P. R. China). Thin-layer chromatography (TLC) was carried out on silica gel precoated plates (Qingdao Haiyang Chemical Co. Ltd.). NMR spectra were measured on Bruker AM-400 spectrometers. Plant Material. Fruits of white pepper (Piper nigrum L.) and long pepper (P. longum L.) were purchased form Anhui Taiyuan Chinese Herbal Pharmacology Co., Ltd. (Voucher No. SCHM 121215). Plant samples were authenticated by Lin Dong of the Pharmacognosy Department, College of Pharmacy, Ningxia Medical University. A voucher specimen was deposited in the same unit (Herbarium number 20141220). Extraction and Isolation. Ethanol (70%) (solid to liquid mass ratio of 1:10) was used to extract residues of supercritical fluid CO2 extract of white pepper and long pepper (20 kg) thrice. The extracting solution was mixed for rotatory evaporation until an alcoholic taste was no longer detected. The yield was the crude extract, which was then successively partitioned with petroleum ether and dichloromethane, ethyl acetate, butyl alcohol, and aqueous residue. The dichloromethane extract was subjected to column chromatography on silica gel (100–200 mesh) eluted with gradient petroleum ether–acetone (from 15:0 to 0:1) to afford fractions 1–9. Fraction 6 was further separated on a Sephadex LH-20 column (methanol as eluent) to afford four subfractions (6-1–6-4). Subfraction 6-1 was chromatographed over an ODS column (methanol–water, 60–100%) and TLC