94 Spectral Assignments and Reference Data Received: 23 August 2007 Revised: 25 September 2007 Accepted: 27 September 2007 Published online in Wiley Interscience: (www.interscience.com) DOI 10.1002/mrc.2119 Structural determination of salsolins A and B, new antioxidant polyoxygenated triterpenes from Salsola baryosma, by 1D and 2D NMR spectroscopy Zaheer Ahmad, a Sajid Mehmood, b Itrat Fatima, c Abdul Malik, c * Rehana Ifzal, a Nighat Afza, b Lubna Iqbal, b Mehreen Latif b and Tanveer Ahmad Nizami c Salsolins A (1) and B (2), the new triterpenes, have been isolated from the chloroform soluble fraction of Salsola baryosma along with 2α,3β ,23,24-tetrahydroxyurs-12-en-28-oic acid (3) reported for the first time from this species. Their structures have been assigned from 1 H and 13 C NMR spectra, DEPT and by 2D COSY, NOESY, HMQC and HMBC experiments. The compounds 1–3 showed significant antioxidant activity. Copyright c  2008 John Wiley & Sons, Ltd. Keywords: NMR; 1D/2D NMR; triterpenes; salsolin A; salsolin B; Salsola baryosma; Chenopodiaceae; antioxidant activity Introduction The genus Salsola (Chenopodiaceae) comprises weedy herba- ceous plants growing mostly on sea shores and the saline soils in temperate regions. In Pakistan this genus is represented by 18 species. [1] The roots of several species of the genus Salsola are commonly used in traditional medicines. The plant is vermifugal and its ashes are applied to itch. [2] Many species of this genus are used as oral contraceptives and in the treatment of skin diseases. [3] These species also possess antibacterial, antifungal and cytotoxic activities. [4,5] Salsola baryosma (syn. S. foetida) is a stout, hoary, pale, excessively branched shrub, which is commonly found in Cholistan desert in Bahawalpur district of Pakistan. Literature sur- vey has revealed that alkaloids, [6] flavonoids and coumarins [7] have so far been reported from this species. The ethnopharmacological and taxonomic importance of this species prompted us to carry out phytochemical studies on S. baryosma. A methanolic extract of this plant showed strong toxicity in brine shrimp lethality test. Fur- ther pharmacological screening revealed significant antioxidant activity in the chloroform soluble subfraction. Bioassay-directed isolation studies on this fraction have now resulted in the isolation of two new polyoxygenated triterpenes named as salsolin A (1) and salsolin B (2) along with 2α,3β ,23,24-tetrahydroxyurs-12-en- 28-oic acid (3) [8] reported for the first time from this species. All of these showed significant antioxidant activity. Results and Discussion The methanolic extract of the whole plant was divided into fractions soluble in n-hexane, chloroform, ethyl acetate, n-butanol and water. Column chromatography of the chloroform soluble fraction provided two new and one known compounds that gave positive result on Lieberman Burchard test for a triterpene and brisk effervescence with dilute sodium bicarbonate solution indicating the presence of free carboxylic group. The new triterpenes have been named as salsolin A (1) and salsolin B (2), respectively. Salsolin A (1) was obtained as a gummy solid. The IR spectrum showed the presence of hydroxyl group (3360 cm −1 ), carboxylic group (1730 cm −1 ) and olefinic bond (1660 cm −1 ). The molecular formula was deduced as C 30 H 48 O 6 through HREIMS, which showed an M + peak at m/z 504.3450 (calcd. for C 30 H 48 O 6 , 504.3445). The molecular formula was further confirmed by the broadband and DEPT 13 C NMR spectra, which showed 30 signals comprising of 5 methyl, 11 methylene, 6 methine and 8 quaternary carbons (Table 1). The downfield signal at δ 181.0 could be assigned to the carboxylic carbon. The presence of one double bond could be inferred by signals at δ 144.4 and 121.3. The signals at δ 76.9 and 69.5 could be ascribed to the oxymethine carbons while two oxymethylene carbons resonated at δ 67.6 and 65.8, respectively. The 1 H NMR spectrum showed the presence of a trisubstituted double bond at δ 5.24 (1H, m). The oxymethine protons were observed at δ 4.20 (1H, m, W 1/2 = 21 Hz) and 3.32 (1H, dd, J = 10.0, 4.1 Hz). The oxymethylene protons were observed at δ 4.12 (1H, d, J = 11.0 Hz), 4.03 (1H, d, J = 10.8 Hz), 3.34 (1H, d, J = 11.0 Hz) and 3.28 (1H, d, J = 10.8 Hz), respectively. The signal at δ 2.13 (1H, dd, ∗ Correspondence to: Abdul Malik, International Center for Chemical Sci- ences, HEJ Research Institute of Chemistry, University of Karachi, Karachi- 75270, Pakistan. E-mail: abdul.malik@iccs.edu a Department of Chemistry, University of Karachi, Karachi-75270, Pakistan b Pharmaceutical Research Centre, PCSIR Labs Complex Karachi, Karachi-75280, Pakistan c InternationalCenterforChemicalandBiologicalSciences,HEJResearchInstitute of Chemistry, University of Karachi, Karachi-75270, Pakistan Magn. Reson. Chem. 2008; 46: 94–98 Copyright c  2008 John Wiley & Sons, Ltd.