## 3 Results and Discussions
### Structural Identification of Alkaloids
Following a similar analysis for the rest of the protons, it was possible to recognize the signals of four major compounds with the core structure of aporphine alkaloids: nonuciferine 1, asimilobine 2, anonaine 3, and isolaureline 4 (Figure 3). Figure 2: \({}^{1}\)H nuclear magnetic resonance spectrum (**bottom**) and homonuclear correlation spectroscopy (COSY) **(top)** spectrum of the alkaloid-enriched F105-150 fractions obtained from the chromatography of the selective extract of alkaloids from _A. muriata_ peel. Cross-correlation contour peaks shown in the COSY experiment (top) allowed to establish vicinal (\({}^{3}\)_J_) and geminal (\({}^{2}\)_J_) \({}^{1}\)H- \({}^{1}\)H connectivity, which concludes that the alkaloid-enriched fraction mainly comprises two pair of aporphine alkaloids (**A**,**B**). The most significant signals showing the presence of these four major alkaloids are described as follows. Between 7.95 to 8.45 ppm can be observed. The signals belong to proton H-8 of these derivatives. Similarly, the signals between 7.20 and 7.35 ppm of the aromatic protons H-9, H-10, and H-11 are grouped, while, in the region of 6.30 to 6.80 ppm, the singlet signals of proton H-3 are observed. The presence of protons for the CH\({}_{2}\) group of the dioxolane ring, assigned as H-12a and H-12b, are also very noticeable between 5.90 and 6.15 ppm. In turn, the singlet signals of methoxy groups (OCH\({}_{3}\)) appear at a higher field between 3.50 and 3.90 ppm. In the same region, the H-6a signal usually appears, which, in this case, is hidden by the rest of the signals. The protons of the piperidine ring (H-4a,b, H-5a,b, and H-6a) appear as complex multiplicity signals in the region between 2.60 and 3.60 ppm. Lastly, in several morphine alkaloids, there is sometimes a CH\({}_{3}\) group directly attached to nitrogen, which appears as a simple signal between 2.30 and 2.60 pm region in which one of these groups is observed (2.54 ppm). The upper trace of the \({}^{1}\)H NMR spectrum (bottom) shows the signals for aromatic protons corresponding to normuciferine 1, assimilobine 2, and anonaine 3 (H-3, H-8, H-9, H-10, and H-11) and isolaureline 4 (H-3, H-8, H-9, and H-11), as well as the protons for dioxolane ring (H-12a and H-12b) of anonaine 3 and isolaureline 4. Bold numbers identify the signals corresponding to each alkaloid according to its identification number. It can be observed that the four double signals (due to scalar coupling with H-9, \(J=8.7\) Hz) belonging to H-8 provided clear evidence that four major alkaloids were present in this mixture. The integral values under each double signal represent the relative ratio between them, which gives 100:44:52:44 from left to right. Complementarily, the four double signals (\(J=1.4\) Hz) shown between 5.90 and 6.15 ppm are typical of geminal protons (H-12a, H-12b) of the dioxolane rings (Figure 2, top, dioxolane derivatives A). A pair of these double signals belong to one alkaloid and the remaining pair belong to another one. Judging by their integral values, both at an averaged ratio of 55:45, it can be deduced that belonging to the same alkaloid gives the double signals appearing in 8.08 (integral 0.53) and 8.01 ppm (integral 0.44) of H-8, respectively. Therefore, it can be concluded that the signals appearing in 8.08, 6.10, and 5.95 ppm belong to protons H-8, H-12a, and H-12b, respectively, of an alkaloid with dioxolane ring (Figure 2, top, A structures) while the signals appearing in 8.01, 6.07, and 5.93 ppm belong to H-8, H-12a, and H-12b, respectively, of the second alkaloid with dioxolane ring. According to this analysis, it can be deduced that the double signals that appear in 8.39 and 8.28 ppm belong to H-8 of two aporphine derivatives without a dioxolane ring (Figure 2, top, B structures).