*2.1. Isolation of Compounds*

The isolation of the compounds presented was based on two main approaches, silica gel and reversed-phase chromatographic separations. Compound **6** was purified as a white amorphous powder, [α] 25D-71 (*c* 0.1, MeOH). HRESIMS of compound **6** showed a molecular ion at *<sup>m</sup>*/*<sup>z</sup>* 687.3967 [M + Na]+ (calculated 687.4047 ± 0.008 *<sup>m</sup>*/*<sup>z</sup>* [M + Na]+ for C37H60O10). The molecular formula of compound **6** was compared with reported triterpenes isolated from *M. charantia* and our in-house database [20]. No match was observed, suggesting an unknown compound. The 13C-NMR spectrum of compound **6** showed resonances of 37 carbons. The 2D-gHMQC spectrum revealed the presence of sixteen methines, seven methylenes, seven methyl, one methoxy, and six quaternary carbons. Six tertiary groups appeared at *δ*H(*δ*c) 0.84 (14.8); 1.74 (26.7); 1.77 (19.1); 1.18 (20.9); 0.87 (24.6); 0.87 (20.6) corresponding to CH3-18, CH3-26, CH3-27, CH3-28, CH3-29 and CH3-30, respectively and one secondary *δ*H(*δ*c) 0.96 (14.7) (d, *J* = 6.4 Hz, CH3-21). The methoxy group was observed at *δ*H(*δ*c) 3.41 s, 3H, assigned as H-1" (58.2, C-1"), one acetal group at *δ*H(*δ*c) 4.70 s, 1H, assigned as H-19 (113.3, C-19), three olefinic protons at *δ*H(*δ*c) 5.98 [dd, *J* = 9.8 Hz, 2.1 Hz, H-6] (132.2, C-6), *δ*H(*δ*c) 5.58 [dd, *J* = 9.8 Hz, 3.4 Hz, H-7] (133.8, C-7) and *δ*H(*δ*c) 5.24 [d, *J* = 10.2 Hz, H-24] (124.6, C-24), and one quaternary olefin carbon *δ*<sup>C</sup> 137.4 (C-25). One anomeric proton at *δ*H(*δ*c) 4.73 [d (*J* = 8 Hz, 1H] (102.6) with a beta linkage corresponding to one hexose appeared in the spectrum together with their respectively five oxygenated signals *δ*H(*δ*c) 3.32, H-2- (73.1, C-2- ), 4.05, H-3- (73.0, C-3- ), 3.48, H-4- (68.5, C-4- ), 3.58, H-5- (75.7, C-5- ) and 3.60, 3.76, H-6- (63.1, C-6- ). 1H and 13C NMR chemical shifts are shown in Table 1.


**Table 1.** 1H and 13C NMR chemical shifts of compound **6**.

Acid hydrolysis of **6** furnished D-allose, which was identified by comparison of the HPLC retention times of thiocarbamoyl thiazolidine derivative with sugar thiocarbamoyl thiazolidine derivative standards [21]. The NMR data of compound **6** suggested the presence of a 5β,19-epoxycucurbitane triterpenes with a methoxy group and a sugar moiety attached [22]. The position of the methoxy group was established through <sup>3</sup>*J* HMBC correlations between *δ*<sup>H</sup> 3.41 ppm (OCH3) and the acetal carbon at position C-19 (*δ*c 113.3), indicating that the methoxy group was attached at C-19.

The relative position of the monosaccharide attachment was confirmed by the assignment of gHMBC spectrum. <sup>3</sup>*J* HMBC correlations between anomeric proton H-1- (4.73 ppm) and C-23 (81.5 ppm) confirmed the attachment of the sugar at C-23. The position of proton H-2 of the allose was confirmed through the 1H-1H COSY correlation between H-2- (4.05 ppm) and the anomeric proton H-1- (4.73 ppm). TOCSY correlations were helpful to identify protons corresponding to the sugar moiety and HMBC, and 1H-1H COSY to

assign remaining proton and carbon chemical shifts. The HMBC correlations between C-24 and CH3-26 and CH3-27; C-25 and H-23, C-22 and H-23 together with C-20 and H-22, suggested that the side chain was -CH(CH3)CH(OH)CH(O-All)=C(CH3)2. Crucial HMBC and 1H-1H COSY correlations are shown in Figure 1A. This type of side-chain has been described previously for karavilosides IV, VIII, IX and X, 23-*O*-β-allopyranosyl-cucurbita-5,24-dien-7α,3β, 22(*R*), 23(*S*)-tetraol 3-O-*β*-allopyranoside; momordicosides M, N and O isolated from *M. charantia* cultivated in Sri Lanka and China [7,23–25]. The stereochemistry of the stereocenters C-22 and C-23 was established by NOESY experiment. A correlation of H-22 was observed with H-21, while no correlation was found for H-22 and H-23 (22S and 22R). C-19 configuration was deduced as *R* due to the correlation between proton H-19 with H-1 and H-2, only observed in *R* configuration (Figure 1B).

**Figure 1.** Crucial HMBC, 1H-1H COSY (**A**) and NOESY correlations (**B**) for compound **6.**

This result was also supported by a comparison of the NMR chemical shifts of H-8, C-8, C-9, C-10, C-11, and C-19 previously reported for several 5β,19*R-* and *S*-epoxycucurbitane triterpenes with different substituents attached at C-19 (methoxy, ethoxy, and hydroxyl groups) [21,26]. However, the main difference in chemical shifts was observed for H-8 and C-8: *R* configuration of H-8 range from 2.82 to 3.37 ppm and from 41 to 43 ppm for C-8, whereas for *S* configuration H-8 (2.13–2.32 ppm) and C-8 (49.5–50.1 ppm). Chemical shifts for compound **6** appeared at H-8 (2.86 ppm) and C-8 (43.2 ppm), supporting the *R* configuration of C-19. Hence, the structure of compound **6** was established as 19(*R*)-methoxy-5β,19-epoxycucurbita-6,24-diene-3β,22*S*,23*R*-triol-23-*O*-β-D-allopyranoside (charantoside XV) and shown in Figure 2.

Compounds **1**–**5** and **7** were identified as known monoglycosides by spectroscopic ( 1H- and 13C-NMR spectra) and spectrometric analyses (HRESIMS), and by comparison with the data reported in the literature as follows: 25ξ-isopropenylchole-5(6)-ene-3-*O*-β-D-glucopyranoside (**1**), karaviloside VI (**2**), karaviloside VIII (**3**), momordicoside L (**4**), momordicoside A (**5**) and kuguaglycoside C (**7**) [7,21,27–29]. Structures of the isolated compounds and 1H- and 13C-NMR data are shown in Figure 2 and the Supporting Information, respectively. This is the first report describing the stereochemistry of the karaviloside VIII side chain to the best of our knowledge. Herein, we described the configuration of the stereocenters C-22 and C-23 through NOESY experiments as 22 *R* and 23*S* since H-22 showed correlation with H-20 and no correlation was observed between H-22 and H-23. Moreover, momordicosides A and L have been isolated from fruits of an Indian cultivar while the other compounds are mainly from Sri Lanka, China, and Japan cultivars. Therefore, this is the first finding of compounds **1**, **2**, **3** and **7** in fruits of the Indian cultivar. On the other hand, kuguaglycoside C was reported as an anticancer agent, showing significant cytotoxicity against human neuroblastoma IMR-32 cells [30]. In the same way, momordicoside A showed weak activity on glucose transport type-4 (GLUT4) on translocation cells [4] and momordicoside L was assayed as a hypoglycemic and antiproliferative compound, showing positive glucose uptake activity and no activity against human breast adenocarcinoma (MCF-7), human medulloblastoma (Doay), human colon adenocarcinoma (WiDr) and human laryngeal carcinoma (HEp-2).

**Figure 2.** Chemical structures of compounds isolated and identified in the present study. (**1**) 25ξ-isopropenylchole-5(6)-ene-3-*O*-β-D-glucopyranoside, (**2**) karaviloside VI, (**3**) karaviloside VIII, (**4**) momordicoside L, (**5**) momordicoside A, (**6**) charantoside XV, and (**7**) kuguaglycoside C.
