Design, Characterization, and Application of a pH-Triggered In Situ Gel for Ocular Delivery of Vinpocetine was written by Ma, Qun;Luo, Rui;Zhang, Huimin;Dai, Manman;Bai, Luyu;Fei, Qingsong;Lei, Fang;He, Ning. And the article was included in AAPS PharmSciTech in 2020.Quality Control of (41S,13aS)-Ethyl 13a-ethyl-2,3,41,5,6,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridine-12-carboxylate This article mentions the following:
Abstract: We developed a pH-triggered in situ gel (ISG) for ocular delivery of vinpocetine to achieve systemic absorption and a brain-targeting effect in rats. Carbopol acted as a gelling agent combined with hydroxypropyl methylcellulose (HPMC) as a viscosity-enhancing agent. The concentration of Carbopol (0.2%, w/v) and HPMC (1.5%, w/v) was optimized for the ISG system. The optimized formulation was evaluated for studies on release in vitro, rheol., differential scanning calorimetry, ocular irritation, residence time, and in vivo pharmacokinetics. The vinpocetine ISG stayed longer in rabbit eyes than vinpocetine ointment. In vivo pharmacokinetics showed that compared with vinpocetine ointment, vinpocetine ISG attained a peak plasma concentration and area under the curve that was 1-2 folds greater in rat plasma. The Drug Targeting Index (DTI) was 1.06 and 1.26 for vinpocetine ointment and vinpocetine ISG, resp., after ocular administration, showing that vinpocetine ISG had better distribution in rat brain. These results revealed that a pH-triggered ISG system via ocular administration could be an alternative approach compared with traditional ophthalmic formulations. In the experiment, the researchers used many compounds, for example, (41S,13aS)-Ethyl 13a-ethyl-2,3,41,5,6,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridine-12-carboxylate (cas: 42971-09-5Quality Control of (41S,13aS)-Ethyl 13a-ethyl-2,3,41,5,6,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridine-12-carboxylate).
(41S,13aS)-Ethyl 13a-ethyl-2,3,41,5,6,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridine-12-carboxylate (cas: 42971-09-5) belongs to naphthyridine derivatives. The naphthyridines have 10 delocalized π-electrons located in five molecular orbitals, each of which is distorted by the presence of the nitrogen atoms causing an electron drift in that direction. 1,6-Naphthyridine and some of its derivatives have been reported to have medicinal, electronic, and catalytic properties. But none of these investigations has yet resulted in any practical applications.Quality Control of (41S,13aS)-Ethyl 13a-ethyl-2,3,41,5,6,13a-hexahydro-1H-indolo[3,2,1-de]pyrido[3,2,1-ij][1,5]naphthyridine-12-carboxylate
Referemce:
1,8-Naphthyridine – Wikipedia,
1,8-Naphthyridine | C8H6N2 – PubChem