Page 233 - Demo

SECTION I: MOLECULAR GENETIC ENGINEERING AND BIOCHEMICAL TECHNOLOGY 237the meta position of ring A [6.44 (1H, d, J = 2.0 Hz, H-6); 6.78 (1H, d, J = 2.5 Hz, H-8)] and 3 protons from the ABX spin system of ring B [6.90 (1H, d, J = 8.0 Hz, H-5%u2032); 7.41 (1H, d, J = 2.5 Hz, H-2%u2032); 7.44 (1H, dd, J = 8.0; 2.0 Hz, H-6%u2032)], along with 1 singlet proton from ring A, suggesting the presence of a luteolin framework similar to compound 1. Additionally, the presence of a glucose unit is characterized by the signal of the anomeric H at dH 5.07 (1H, d, J = 7.5 Hz, H-1%u2033) and 6 protons at 3.18 (1H, t, J = 8.0 Hz, H-4%u2033); 3.27 (1H, m, H-2%u2033); 3.29 (1H, m, H-3%u2033); 3.44 (1H, m, H-5%u2033); 3.47 (1H, m, H-6%u2033a); 3.71 (1H, dd, J = 11.5; 1.5 Hz, H-6%u2033b). The coupling constant JH-1%u02ba,H-2%u02ba = 7.5 Hz indicates that H-1%u02ba and H-2%u02ba are both in the axial position, characteristic of a %u03b2-D-glucoside bond. Correspondingly, in the 13C-NMR spectrum of compound 2, signals for 21 carbon atoms appear. Among them, 14 aromatic carbon atoms have chemical shifts dC in the range of 94.7 to 164.4 ppm and 1 carbonyl group at dC 181.8 is assigned to the flavone framework; the remaining 6 carbon atoms are assigned to the glucopyranose molecule at dC 60.6 (C-6%u2033); 69.5 (C-4%u2033); 73.1 (C-2%u2033); 76.4 (C-3%u2033); 77.1 (C-5%u2033) and 99.9 (C-1%u2033). The attachment position of the glucose molecule at C-7 on the flavone framework was determined based on the interaction between H-1%u02ba (5.07 ppm) and C-7 (162.9 ppm) obtained from the two-dimensional HMBC spectrum. Based on the analysis of the spectral data obtained for compound 2, combined with a comparison with the literature [9], compound 2 was identified as luteolin-7-O-glucoside. Several studies worldwide have indicated that luteolin-7-O-glucoside exhibits antioxidant, antiviral and antibacterial activities [9]. Compound 3 was obtained as a yellow powder. The 1H-NMR spectrum of compound 3 reveals the presence of 5 aromatic protons with chemical shifts %u03b4H at 7.69 (1H, d, J = 2.5 Hz, H-2%u2032); 7.65 (1H, dd, J = 8.5; 2.0 Hz, H-6%u2032); 6.90 (1H, d, J = 8.5 Hz, H-5%u2032); 6.42 (1H, d, J = 2.0 Hz, H-8) and 6.23 (1H, d, J = 2.0 Hz, H-6), along with