Ephedra sinica, an important plant in Chinese traditional medicine, contains a complex mixture of proanthocyanidin oligomers as major constituents; however, only the minor components have been chemically characterized. In this study, oligomers with relatively large molecular weights, which form the main body of the proanthocyanidin fractions, were separated by adsorption and size-exclusion chromatography. Acid-catalyzed degradation in the presence of mercaptoethanol or phloroglucinol led to the isolation of 18 fragments, the structures of which were elucidated from their experimental and TDDFT-calculated ECD spectra. The results indicated that (−)-epigallocatechin was the main extension unit, while catechin, the A-type epigallocatechin–gallocatechin dimer, and the A-type epigallocatechin homodimer, were identified as the terminal units. Among the degradation products, thioethers of gallocatechin with 3,4-cis configurations, a B-type prodelphinidin dimer, a prodelphinidin trimer with both A- and B-type linkages, and a prodelphinidin dimer with an α-substituted A-type linkage were new compounds. In addition, a phloroglucinol adduct of an A-type prodelphinidin dimer, a doubly-linked phloroglucinol adduct of epigallocatechin, and a unique product with a flavan-3-ol skeleton generated by the rearrangement of the aromatic rings were also isolated.

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Neurological disorders remained the leading cause of long-term disability and the second leading cause of death in 2019, hence there is an urgent need for new neuropharmacological agents. P. ophthalmicus is a Philippine medicinal plant with reported antibacterial, antitubercular, and COX-2 inhibitory activities which have recently been attributed to its alkaloids (+)-tetrandrine and limacusine. It also contains phaeantharine, phaeanthine, oxostephanine, and O-methyldauricine which are alkaloids with a benzylisoquinoline moiety also present in the known neuroactive drugs papaverine, morphine, and tubocurarine. As of this writing, there have been no investigations into the neuropharmacological uses of these alkaloids yet. Therefore, extensive molecular docking studies using Discovery Studio software were conducted. Our findings identified 4MF3 (Kainate 1), 5O8F and 6HUK (GABAA), and 6G79 (Serotonin 1B) as potential neuroreceptor targets, which are involved with pain, migraine, stroke, epilepsy, and anxiety, among other neurological disorders. Furthermore, 50 out of 232 generated analogs of the alkaloids displayed better docking scores, novelty, and predicted drug-likeness. It was observed that the replacement of the methoxy groups attached to the bisbenzylisoquinoline moiety generally resulted in better binding. Lastly, a particular corydaldine analog is considered a very promising oral neuropharmacological agent after displaying consistent top docking scores across all neuroreceptors, drug-likeness, and favorable pK profiles in silico. Therefore, synthesis of such analog and follow-up in vitro-in vivo studies are highly suggested by the researchers.

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