Phytochemicals variation between hydrochloric and tartaric acid-derived alkaloidal extracts of Erythrina fusca Lour. Leaves: A proton NMR-based approach

• Published in: South African Journal of Botany
• Main Author: Azmi A.S.; Mediani A.; Abidin W.A.M.W.Z.; Othman W.N.N.W.; Cordell G.A.; Salim F.
• Format: Article
• Language: English
• Published: Elsevier B.V. 2024
• Online Access: https://www.scopus.com/inward/record.uri?eid=2-s2.0-85189452491&doi=10.1016%2fj.sajb.2024.03.040&partnerID=40&md5=fcb8d6f9db9c0a9cc3ea7e6733f59df4

Erythrina fusca Lour. (Fabaceae) has been used traditionally to relieve toothache and migraine headaches, cleansing putrid ulcers, and reducing skin inflammations and irritation. Interestingly, most of the reported biological activities on the plant are attributed to its Erythrina alkaloids which are usually extracted through the acid-base method. While the selection of acids for the extraction process is crucial, there is limited information on comparing the efficacy of strong organic and inorganic acids in extracting Erythrina alkaloids, and, more broadly, other types of alkaloids. In this study, comparison between hydrochloric acid (HCl) and tartaric acid (H2T) was made to extract the Erythrina alkaloids. From the same mass (10 g) of the crude methanolic leaf extract, a significantly higher (9-fold) alkaloidal yield was obtained using H2T compared to the HCl. The alkaloidal extracts displayed different proton nuclear magnetic resonance (1H NMR) profile where identification of their phytochemical constituents was done extensively through comparison with respective data of previously isolated compounds from the Erythrina species. Forty-seven phytochemicals were identified in the HCl extract and they were mostly alkaloids. While the H2T extract not only contained alkaloids, but also flavonoids, and pterocarpans. Cumulatively, 83 phytochemicals were identified from the extracts, including 35 alkaloids, 18 flavonoids, 14 pterocarpans, 9 terpenes, 3 phenols, and 4 saponins. Based on multivariate analysis (MVDA), the alkaloids erysodine (1), erysovine (2), erysopine (3), warangalone (39), calopocarpin (53), and dolichin A (60) were found in both alkaloidal extracts. The PLS-DA model further identified the variation in the two extracts where the HCl extract was characterized by the flavonoids lupinifolin (41) and erythrisenegalone (43). Conversely, the H2T extract contained a broader range of phytochemicals, including the alkaloids glucoerysodine (21) and erythratidinone (28), the flavonoids 5,3′-dihydroxy-4′‑methoxy-5′-(3-methyl-1,3-butadienyl)-2′′,2′′dimethylpyrano-[5,6:6,7]-isoflavanone (51), 5,3′-dihydroxy-5′-(3‑hydroxy-3-methyl-1-butenyl)-4′‑methoxy-2′′,2′′dimethylpyrano-[5,6:6,7]-isoflavanone (52), and catechin (82), the pterocarpans calopocarpin (53) and sandwicensin (63), the terpenes loliolide (70), ursolic acid (80), propyloxyamyrin (83), and stigmast-3-en-4-one (73), the saponins sigmoisides A, B, and E (75, 76, and 77), and the phenol methyl gallate (81). The present findings highlight the value of targeting the extraction process for alkaloids, in this instance Erythrina alkaloids, using different type of acids. Furthermore, these compounds may be considered potential markers that were selectively extracted through the acid-base extraction process. © 2024 SAAB