A neoclerodane orthoester and other new neoclerodane diterpenoids from Teucrium yemense chemistry and effect on secretion of insulin

Mohammad Nur-e-Alam, Ifat Parveen, Barrie Wilkinson, Sarfaraz Ahmed, Rahman M. Hafizur, Ahmed Bari, Timothy Woodman, Michael Threadgill, Adnan J. Al-Rehaily

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Teucrium yemense, a medicinal plant commonly grown in Saudi Arabia and Yemen, is traditionally used
to treat infections, kidney diseases, rheumatism, and diabetes. Extraction of the dried aerial parts
of the plant with methanol, followed by further extraction with butanol and chromatography, gave
twenty novel neoclerodanes. Their structures, relative confgurations and some conformations were
determined by MS and 1-D and 2-D NMR techniques. Most were fairly conventional but one contained
an unusual stable orthoester, one had its (C-16)–(C-13)–(C-14)–(C-15) (tetrahydro)furan unit present as
a succinic anhydride and one had a rearranged carbon skeleton resulting from ring-contraction to give
a central octahydroindene bicyclic core, rather than the usual decalin. Mechanisms are proposed for
the biosynthetic formation of the orthoester and for the ring-contraction. Four novel neoclerodanes
increased the glucose-triggered release of insulin from isolated murine pancreatic islets by more than
the standard drug tolbutamide, showing that they are potential leads for the development of new
anti-diabetic drugs.
Original languageEnglish
Article number8074
JournalScientific Reports
Publication statusPublished - 13 Apr 2021

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