Two novel oxetane containing lignans and a new megastigmane from Paronychia arabica and in silico analysis of them as prospective SARS-CoV-2 inhibitors

Abstract

The hydromethanolic extract of Paronychia arabica aerial parts afforded two oxetane containing lignans, paronychiarabicine A (1) and B (2), and one new megastigmane, paronychiarabicastigmane A (3), alongside a known secondary metabolites (4–14).

Reassignment of Improbable Natural Products Identified through Chemical Principle Screening

“…However, considering the overall NMR chemical shift similarity between 9 and 10 , this aspect required additional physical property comparison. As reported by Elshamy et al [32] . there is a factor of three difference in the optical rotation when comparing 9 against 10 (i. e. paronychiarabicine A is −5.1 and for B it is −15.6).…”

“…[37] However, considering the overall NMR chemical shift similarity between 9 and 10, this aspect required additional physical property comparison. As reported by Elshamy et al [32] there is a factor of three difference in the optical rotation when comparing 9 against 10 (i. e. paronychiarabicine A is À 5.1 and for B it is À 15.6). Therefore, given the optical rotation reported by Ichihara et al for lappaol A (-17.4 [38] ) which matches that obtained (i. e., À 15.6) for paronychiarabicine B (10), 9 and 10 should be reassigned as isolappaol A (23) and lappaol A (24), respectively (Figure 3).…”

“…Paronychiarabicine A ( 9) and B (10). The isolation of 9 and 10 from the aerial parts of Paronychia arabica was recently reported by Elshamy et al [32] Although the oxetane moiety has previously been observed in natural products, many have recently been reassigned as other functionality, [33] making this structural unit rare (e. g., taxol [34] ) and a target for potential erroneous structure elucidation. ACD/SE generated a ranked solution (see Figures S5-S7 in SI) from the 2D NMR data input for paronychiarabicine A (9), which gave as the first ranked structure a skeletal framework closely matching known lignans, whereby a dihydrobenzofuran moiety replaced the oxetane ring (i. e., 22) (Figure 3).…”

“…Paronychiarabicine A ( 9 ) and B ( 10 ) . The isolation of 9 and 10 from the aerial parts of Paronychia arabica was recently reported by Elshamy et al [32] . Although the oxetane moiety has previously been observed in natural products, many have recently been reassigned as other functionality, [33] making this structural unit rare (e. g., taxol [34] ) and a target for potential erroneous structure elucidation.…”

Anti-SARS-CoV-2 and cytotoxic activity of two marine alkaloids from green alga Caulerpa cylindracea Sonder in the Dardanelles

“…Therefore, several publications of new anti-viral agents derived from synthetic and natural sources including repurposing studies have been made and are still going on to be published. [2][3][4] Seaweeds have been consumed as food by humans for centuries, and the present worldwide market is worth more than $6 billion per year, with an annual volume of around 12 million tonnes in 2018. Macroalgae are prevalent in coastal ecosystems and provide a source of bioactive metabolites with a variety of potential and noteworthy biological activities, capable of impacting the abundance, distribution, and survival of marine organisms.…”