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Two new aliphatic lactones from the fruits of Coriandrum sativum L. Abstract Background: The present paper describes the isolation and characterization of two new aliphatic δ-lactones along with three glycerides and n-nonadecanyl cetoleate from the fruits of Coriandrum sativum L. (Apiaceae). The structures of all the isolated phytoconstituents have been established on the basis of spectral data analysis and chemical reactions. Results: Phytochemical investigation of the methanolic extract of C. sativum L. (Apiaceae) fruits resulted in the isolation of two new aliphatic δ-lactones characterized as 2α-n-heptatriacont-(Z)-3-en-1,5-olide (1) (coriander lactone) and 2α-n-tetracont-(Z,Z)-3,26-dien-18α-ol-1,5-olide (2) (hydroxy coriander lactone) together with


Background
Coriandrum sativum L. is an annual and herbaceous plant belonging to the Apiaceae family. It is a medicinal plant, native of southern Europe and western Mediterranean region and is cultivated worldwide [1]. India is the largest producer of coriander in the world. Major production centers are Rajasthan, Maharastra, Gujarat, and Karnataka [2]. The whole plant and especially the unripe fruits are characterized by a strong disagreeable odor, hence the name coriander, giving characteristic aroma when rubbed [3]. The most important constituents of coriander seeds are the essential oil and the fatty oil. The dried coriander seeds contain an essential oil (0.03% to 2.6%) with linalool as main component [4,5], phenolics, flavonoides [6], and isocoumarin compounds [7]. It has traditionally been referred to as antidiabetic [8] and cholesterol lowering drug [9,10]. This paper describes the isolation and characterization of two new aliphatic δ-lactones along with fatty acid glycerides, ester, and glucoside from the fruits of C. sativum of Delhi region of India.

General
Melting points were determined on a Perfit melting apparatus (Ambala, Haryana, and India) and are uncorrected. UV spectra were measured with a Lambda Bio 20 spectrophotometer (Perkin-Elmer-Rotkreuz, Switzerland) in methanol. Infrared spectra were recorded on Bio-Rad FTIR 5000 (FTS 135, Kowloon, Hong Kong) spectrophotometer using KBr pellets; γ max values are given in cm −1 . 1 H nuclear magnetic resonance (NMR) and 13 C NMR spectra were screened on Bruker spectrospin 300 and 75 MHz, respectively, instruments (Karlesruthe, Germany) using CDCl 3 and TMS as an internal standard. Mass spectra were measured by effecting fast atom bombardment (FAB) ionization at 70 eV on a JEOL-JMS-DX 303 spectrometer (JEOL, Japan) equipped with direct inlet probe system. Column chromatography was performed on silica gel (60 to 120 mesh; Qualigen, Mumbai, India). TLC was run on silica gel G (Qualigen, Carlsbad, CA). Spots were visualized by exposing to iodine vapors, UV radiation, and spraying with ceric sulphate.

Results and discussion
Compound 1, named coriander lactone (Scheme 1), was obtained as a pale yellow crystalline mass from petroleum ether eluents. Its IR spectrum showed characteristic absorption bands for δ-lactone group (1738 cm −1 ), unsaturation (1621 cm −1 ), and long aliphatic chain (806, 721 cm −1 ). On the basis of FAB mass spectrum, its molecular weight was established at m/z 546 consistent with the molecular formula of an unsaturated lactone, C 37 H 70 O 2 . It indicated three double bond equivalents; two of them were adjusted in the lactone ring and remaining one in the vinylic linkage. The prominent ion peaks arising at m/z 97 [C 2 -C 6 fission, C 5 H 5 O 2 ] + and 449 [M-97, (CH 2 ) 31 CH 3 ] + suggested that δ lactone was attached to the C-32 aliphatic chain. The 1 H NMR spectrum of 1 showed a one-proton double doublet at δ 5.36 (J = 6.6, 7.2 Hz) and a one-proton multiplet at δ 5.32 assigned to (Z)-vinylic H-3 and H-4 protons, respectively. A two-proton doublet at δ 4.14 (J = 7.2 Hz) was ascribed to oxygenated methylene H 2 -5 protons. A one-proton broad multiplet at δ 2.78 with half width of 6.1 Hz was attributed to β-oriented H-2 methine proton. A two-proton multiplet at δ 2.30, two four-proton multiplets at δ 2.05 and 1.59, and a broad signal at δ 1.26 integrating for 52 protons were associated with the methylene protons. A three-proton triplet at δ 0.90 (J = 6.3) was accounted to C-37 primary methyl protons. Compound 2, named hydroxy coriander lactone, was obtained as a pale yellow crystalline mass from chloroform eluents (Scheme 2). Its IR spectrum showed distinctive absorption bands for a hydroxy group (3463 cm −1 ), lactone ring (1743 cm −1 ), unsaturation (1645 cm −1 ), and long aliphatic chain (722 cm −1 ). Its These evidences led to formulate the structure of 2 as 2α-n-tetracont-(Z,Z)-3, 26-dien-18α-ol-1,5-olide. This is a new δ-lactone isolated from a plant source.

Plant material
The fruits of C. sativum were collected from the herbal garden of Jamia Hamdard, New Delhi. The plant material was identified by Prof. MP Sharma, Taxonomist, Department of Botany, Faculty of Science, Jamia Hamdard, New Delhi. A voucher specimen (PRL/JH/07/27) of drug is preserved in the Phytochemistry Research Laboratory, Department of Pharmacognosy and Phytochemistry, Faculty of Pharmacy, Jamia Hamdard, New Delhi.

Extraction
C. sativum fruits (1.6 kg) were dried in air and then in an oven at 45°C temperature. The material was coarsely powdered. Exhaustive extraction of powdered drug was carried out in a Soxhlet apparatus using methanol as extracting solvent. The methanolic extract was concentrated under reduced pressure to yield a dark brown viscous mass, 187 g (11.68%).

Isolation of phytoconstituents
The methanolic extract (85 g) was dissolved in a minimum amount of methanol and adsorbed on silica gel (60 to 120 mesh) for preparation of slurry. The air-dried slurry was chromatographed over the silica gel column packed in petroleum ether (60 to 80°C). The column was eluted with petroleum ether (60 to 80°C), chloroform, and methanol in order of increasing polarity to isolate the following compounds: