Complete Structural Assignment of Serratol, a Cembrane-Type Diterpene from Boswellia serrata, and Evaluation of Its Antiprotozoal Activity

Abstract

From the dichloromethane extract obtained from the gum resin of Boswellia serrata Roxb. (Burseraceae), a well-known medicinal plant resin (“Indian Olibanum”), the cembrane-type diterpene serratol was isolated in high yield. Its structure, previously reported without clear specification of double-bond geometry and without specification of stereochemistry, was reanalysed by means of spectroscopic measurements and unambiguously assigned as S(−)-cembra-3E,7E,11E‐triene-1-ol. Full assignment of all NMR data is reported for the first time. The compound was found to be identical with a cembrenol previously isolated from B. carteri. Serratol was tested for in vitro activity against four protozoan human pathogens, namely, Trypanosoma brucei rhodesiense (East African Human Trypanosomiasis, sleeping sickness), T. cruzi (Chagas' disease), Leishmania donovani (Kala-Azar), and Plasmodium falciparum (Tropical Malaria). It was found active against T. brucei and P. falciparum. These activities were 10- to 15-fold higher than its cytotoxicity against rat skeletal myoblasts. While some reports exist on potential anti-inflammatory activity of Boswellia diterpenes, this is the first report on antiprotozoal activity of such a compound.

Key words

Boswellia serrata Roxb. - Burseraceae - cembrane diterpene - serratol - antiprotozoal activity

References

• 1 Pardhy R S, Bhattacharyya S. Structure of serratol, a new diterpene cembranoid alcohol from Boswellia serrata Roxb.  Indian J Chem. 1977;  16 B 171-173
• 2 Klein E, Obermann H. (S)-1-Isopropyl-4,8,12-trimethyl-cyclotetradeca-3E,7E,11E-trien-1-ol, ein neues Cembrenol aus dem ätherischen Öl von Olibanum.  Tetrahedron Lett. 1978;  4 349-352
• 3 Kobayashi M, Osabe K. Marine terpenes and terpenoids. VII. Minor cembranoid derivatives, structurally related to the potent anti-tumor-promoter sarcophytol A, from the soft coral Sarcophyton glaucum.  Chem Pharm Bull. 1989;  37 631-636
• 4 Moussaieff A, Shohami E, Kashman Y, Fride E, Schmitz M L, Renner F, Fiebich B L, Munoz E, Ben-Neriah Y, Mechoulam R. Incensole acetate, a novel anti-inflammatory compound isolated from Boswellia resin, inhibits nuclear factor-kB activation.  Mol Pharmacol. 2007;  72 1657-1664
• 5 Moussaieff A, Shein N A, Tsenter J, Grigoriadis S, Simeonidou C, Alexandrovich A G, Trembovler V, Ben-Neriah Y, Schmitz M L, Fiebich B L, Munoz E, Mechoulam R, Shohami E. Incensole acetate: a novel neuroprotective agent isolated from Boswellia carterii.  J Cereb Blood Flow Metab. 2008;  28 1341-1352
• 6 Nour A M M, Khalid S A, Brun R, Kaiser M, Schmidt T J. The antiprotozoal activity of sixteen Asteraceae species native to Sudan and bioactivity-guided isolation of xanthanolides from Xanthium brasilicum.  Planta Med. 2009;  75 1363-1368
• 7 Nour A M M, Khalid S A, Brun R, Kaiser M, Schmidt T J. The antiprotozoal activity of methylated flavonoids from Ageratum conyzoides L.  J Ethnopharmacol. 2010;  129 127-130