Identification of a Rare Phytosteroid from Justicia gendarussa

Abstract

Justicia gendarussa L. (Acanthaceae) is an evergreen, shade-loving, highly branched shrub. Traditionally, the plant is used in the treatment of rheumatism, dysuria, fever, carbuncles, jaundice, diarrhea, pains in the head, ear, paralysis, bruises, etc. [1, 2]. Previous reports on the pharmacological studies revealed the antioxidant, antiarthritic, antiinflammatory, analgesic, antinociceptive, antifertility, anticancer, hepatoprotective, and larvicidal properties of this plant [3–5]. Numerous chemical constituents such as sterols, flavonoids, alkaloids, reducing sugars, and O-methyl ethers of benzyl alcohol were reported from J. gendarussa leaf samples [6–8]. The present study led to the discovery of a new phytosteroid in the stem as well as callus sample of J. gendarussa. The stem samples of J. gendarussa were collected from natural forests of Dakshina Kannada District, Karnataka, India and the voucher specimen (MU/AB/BN-01) was deposited at the Herbarium of Department of Applied Botany. The callus was initiated on Murashige and Skoog medium supplemented with -naphthalene acetic acid and benzyl amino purine (1.0 + 0.1 mg/L) from the sterilized stem explants, cultured in liquid medium and harvested on the 35th day [9]. The sample was dried, extracted in ether using a Soxhlet apparatus for 8–10 h, and concentrated to dryness at 40 C. The dried extract was separated in TLC (silica gel G 60 F 254, Merck, India) using acetic acid:chloroform as solvent system. The clear spot obtained on the chromatogram was separated from the silica gel, redissolved in ether, and dried. The amorphous powder obtained was used for spectroscopic analysis using UV, FTIR, 1H NMR, and LC-MS/MS. The LC-MS analysis was performed in a Thermo Finnigan Surveyor-Thermo LCQ Deca XP MAX system with a BDS Hypersil C18 column (250 mm 4.6 mm), 100% MeOH as eluent, at ambient temperature, nebulization gas helium, and electron spray ionization method with UV and PDA as detectors. The data obtained from the LC-MS/MS spectrum were compared and predicted using NIST (National Institute of Standards and Technology, Gaithersburg, MD), version 2.0a, 2002 software. Based on all the spectral data obtained, the colorless amorphous compound was predicted as a phytosteroid: 1 -carboethoxy-1 -cyano-1,2-dihydro-[1,2]cyclopropcholest-3-one (1) with an elemental composition of C32H49NO3, m/z 496 [M + H] + by ESI-MS/MS. 1 -Carboethoxy-1 -cyano-1,2-dihydro-[1,2]cycloprop-cholest-3-one (1) was isolated as a amorphous powder. The UV spectrum of the compound in ether showed absorption maxima ( max) at 282 nm, and the FTIR spectrum of the compound in KBr exhibited absorption at ( ) 1743 and 1653 cm–1 for the ester and free carbonyl groups (C=O), 2370 cm–1 for the N C group, 3450 cm–1 for -OH or -NH stretch, and 2924 cm–1 for C-H stretching. In the 1H NMR (400 MHz, MeOD, , ppm) the ethyl protons of the carboethoxy moiety appeared as a triplet and a quartet centered at 2.30 and 4.16, integrating for three and two protons, respectively. The signal due to the protons attached to the cyclopropane ring appeared as doublets at 2.05 and 2.32, integrating for one proton each. The signal due to the two methyl and the methyl groups of the isopropyl moiety overlapped with each other and appeared in the region of 0.9–1.3, integrating for 12 protons. However, the signal due to other protons overlapped with each other and appeared as multiplets in the region of 0.875–4.5. The ESI-MS/MS spectrum (ESI, 4.5 kV) showed the molecular ion peak [M + H]+ at m/z 496, consistent with the proposed molecular formula of the phytosteroid C32H49NO3. Spectroscopy was used for the detection of phytosterols in the callus tissue of Cissus quadrangularis [10], ursane type triterpenes in Olea europaea [11] and azadirachtin in cell suspension cultures of Azadirachta indica [12], triterpenoid glycosides in Justicia betonica [13], flavonoids in Punica granatum [14], and triterpenes and sesquiterpenes in Pinus densata