## 3 Results and Discussions
### Structural Identification of Alkaloids
It can also be observed in Figure 4 where the \({}^{13}\)C NMR spectrum (bottom) shows the set of signals for aromatic carbons (\(\delta\) 105-160), acetalc carbons of the dioxolane ring (\(\delta\) 100.7-100.8), C-6a and OCH\({}_{3}\) groups (\(\delta\) 53-65), and in a higher field (\(\delta\) 28-47) N-CH\({}_{3}\), C-5, and C-4 carbons. The heteronuclear single quantum correlation (HSQC) experiment allowed to stablish de one-bond (\({}^{1}\)\(J\)) heteronuclear correlation between protons attached to their respective carbons (Figure 3, top). Both experiments complement  
Figure 3: Basic structure of aporphine alkaloids with its systematic numbering (**left**), present in several species of genus _Anmona_. The isoquinoline nucleus is shown in red. Structures of the major alkaloids (**right**) identified in alkaloid-enriched fractions F105-F150 obtained from the fruit of _Anmona muricata_. the spectroscopic evidence that the alkaloid-enriched fractions contain the presence of the following four compounds: nonuciferine 1, asimilobine 2, anonaine 3, and isolaureline 4. As mentioned above, such compounds possess the core structure of tetracyclic alkaloids named aporphine, which are biogenetically referred to as isoquinoline derivatives. Figure 4: Heteronuclear single quantum correlation (HSQC, **top**) and \({}^{13}\)C nuclear magnetic resonance (NMR) spectrum (**bottom**) of the alkaloid-enriched F105-150 fractions obtained from the chromatography of the selective extract of alkaloids from _A. muricata_ peel. HSQC experiment shows one-bond correlations for all protonated carbons and help discriminate all non-protonated carbons. \({}^{13}\)C NMR spectra (**bottom**) shows the range of chemical shifts in which the different types of carbons belonging to alkaloids normuciferine 1, assimilobine 2, anonaine 3, and isolaureline 4 appear. Bold numbers identify the signals corresponding to each alkaloid according to its identification number. Once the typical NMR signals of aporphine alkaloids were recognized, a bibliographic review was made on alkaloids present in the fruit of _A. muricata_ in order to compare the information of our spectra with those described in the literature. With these considerations in mind, we proceeded to review the NMR data described for aporphine alkaloids isolated from the _A. muricata_ fruit, or from other parts of this plant, including other species. Thus, [PERSON] et al. [6; 7] described the isolation of alkaloids nonnuciferine 1, asimilobine 2, and anonaine 3 from _A. muricata_ fruits, along with their respective \({}^{1}\)H and \({}^{13}\)C NMR data. The former (\({}^{1}\)H NMR data) coincided faithfully with those observed in Figure 2. Although [PERSON] et al. [6; 7] does not describe the structure of isolaureline 4, it was possible to determine that this derivative contains an OCH\({}_{3}\) group attached at C-10 since the chemical shifts of H-8 and H-9 are shifted to higher field due to the donor effect of the OCH\({}_{3}\) group. In addition, multiplicity of H-9 (dd, \(J\) = 8.5, 1.9 Hz) corresponded to an _ortho_ coupling with H-8 and _meta_ with H-11. The rest of the functional groups were very similar to those present in annoanine 3. It was also found that isolaureline 4 was already described by [PERSON] and [PERSON] [33] as a product of synthesis. Years later, this compound was isolated for the first time from a plant by [PERSON] et al. [34]. Although \({}^{1}\)H and \({}^{13}\)C NMR data of isolaureline 4 are not fully described to date, the NMR data collected in this paper are sufficient to propose that this alkaloid is also present in this mixture from _A. muricata_ peel, since no such alkaloids have been reported in this raw material. For now, the present results motivate to apply the present protocol to extract, purify, quantify, and determine the structure and relative ratio of the minor and major alkaloids present in other organs of _Anonona_ species.