The root of has been used in China for centuries as the medicinal herb and identified their structures using spectroscopic analyses. that some of the natural tetrahydroanthraquinones in HG are bioactive, and hydroxylation at C-1 significantly increases the cytotoxicity of these compounds against lung tumor cell growth. in Hz)in Hz)in Hz)in Hz)in Hz)in Hz)in Hz)in Hz)] in CDCl3 at 600 MHz; c overlapped. 2.1. Chemical Structure of Prisconnatanones C to I (Compounds 355.1152 and 13C-NMR spectroscopy (Table 1), showing nine degrees of unsaturation. The infrared (IR) spectrum displayed the presence of hydroxy (3441 cm?1), conjugated carbonyl (1655 cm?1), and aromatic ring groups (1610, 1577, and 1459 cm?1) in GS-9973 cost this compound. Based on a previous study [11] the UV spectrum suggested that there might be an anthraquinone chromophore, according to the presence of absorption peaks at 210, 268, 362 nm. The 13C-NMR spectrum revealed 18 characteristic signals indicating two quinone carbonyl groups (C 184.2, 183.3) on positions 9 and 10, eight aromatic or olefinie carbons (C 157.3, 154.3, 147.9, 145.0, 139.8, 129.7, 119.7, 106.1), five sp3 carbons (C 71.0, 34.2, 30.9, 29.9, 17.5) and three methoxy groups (C 61.8, 61.6, 56.6) (Table 1). The 1H-NMR data showed an aromatic proton H 7.42 (1H, s), and three methoxyls (H 3.97, 3.93, 3.90, every 3H, s) (Table 2). In the comparison with the published data of prisconnatanone A [9], both the 1H-NMR and 13C-NMR data were similar, suggesting that compound 1 was also a tetrahydroanthraquinone. Analysis of 1D NMR, 1H-1H COSY, and HSQC data revealed the presence of one 2-hydroxy-3-methylbutane unit and one pentasubstituted nephthoquinone moiety. The methyl (C 17.4) was confirmed to be at C-3 by 1H-1H COSY (Figure 2), cross-peaks (from H-3 to H3-Me, H-2, H-4, from H2-1 to H-2) and HMBC correlations (from H3-Me to C-2, C-3, and C-4) (Figure 2). The aromatic proton H 7.42 (1H, s) showed HMBC correlations with C-9 ( 184.2), C-12 ( 119.7), C-7 ( 157.3), suggesting that C-8 was unsubstituted and the three methoxy groups (C 61.8, 61.6, 56.6) were located at C-5, C-6 and C-7. Therefore, the planar structure of compound 1 was identified as 1,2,3,4-tetrahydro-2-hydroxy-5,6,7-trimethoxy-3-methylanthracene-9,10-dione (Figure 1). A single crystal of compound 1 was obtained by slow crystallization in methanol and water, and was mounted on a X-ray diffractometer equipped with Cu K monochromated radiation, which allowed the compound structure to be unequivocally determined with OH-2, Me-3 in a relationship (Figure 4). The absolute configuration of the chiral centers at C-2 and C-3 of 1 1 was assigned as 2and 3by using Hooft methods, which were further confirmed by GS-9973 cost application of the advanced Moshers method (Figure 5). Therefore, compound 1 was trivially named as prisconnatanone C and unequivocally identified as (2has been reported. Open in a separate window Figure 4 X-ray crystal structure of compound 1. Open in a separate window Figure 5 (S-R) values (in ppm) for the MTPA esters of 1 1. 1a R = (S)-MTPA; 1b R = (R) ? MTPA. Compound 2 showed a pseudomolecular [M + Na]+ ion peak at 355.1156, indicating the same molecular formula C18H20O6 as GS-9973 cost 1 based on the HRESIMS data. By comparison of their 1D NMR (Table 1 and Table 2), there were slight differences in two aromatic carbons and two methylene groups (Figure 1): 1 with (C Nos1 145.0, 139.8, 30.9, 29.9) and 2 with (C 143.6, 141.2, 31.3, 29.4). Further, HMBC correlations from H-5 to C-6, C-10 and C-11 were observed in 2, revealing that the C-5 was unsubstituted and the three methoxy groups (C 56.6, 61.6, 61.8) were located at C-6, C-7 and C-8 (Figure 2). Besides, a 3= ?55.7 (= 0.16, MeOH), had the similar sign and magnitude as seen in 1, = ?61.7 (= 0.2, MeOH), suggesting the same absolute configurations at C-2 and C-3. Thus, compound 2 was identified as (2385.1258, indicating a.