Phytochemical analysis and antimicrobial evaluation of Dolichandrone spathacea (Bignoniaceae)

Dolichandrone spathacea (L.f.) K. Schum. named “mangrove trumpet tree” is a common smooth tree growing wild in riverbanks and mangroves of the Asia-Pacific area. The leaves of this traditional medicinal plant are used in different countries to treat oral thrush (as mouthwash), flatulence and bronchitis (juice of leaves) [1, 2, 3]. The sole report on the plant found in the literature mentioned the detection of flavonoids, triterpenes and tannins [4].

Chemical investigation of the methanolic extract of leaves of a sample collected in Vietnam, furnished 16 iridoids, 3 saponins, 3 phenylethanoid glycosides, 4 flavonoid glycosides, 3 monoterpenic acids, 5 phenolic acids and 1 megastigman glucoside. Their structures were established by spectral means, particularly extensive 2D NMR and MS-MS, and from partial hydrolysis. Among these compounds, five are new.

With regard to the traditional use of the leaves against various infections and according to literature results on the antimicrobial activity of the methanolic extract against MRSA [4], we set to study our material along these lines. Thus, the antimicrobial activity of five extracts and of all isolated compounds was evaluated against 22 microorganisms using methods such as bioautography, measurement of MIC (minimum inhibitory concentration) on microplates, and screening using a multiple inoculator (Steers) [5]. At variance with most of the literature, we chose to determine the MIC against a large spectrum of microorganisms in order to discover extracts with a broad-scale activity.

The results reveal for the first time the presence in this species of several new natural compounds with an interesting level of antimicrobial activity (the lowest MIC = 31.2 µg/ml). The synergy (activity for mixtures of compounds) and in vivo studies with these compounds may be interesting in the future for a valorization approach.

Acknowledgements: J. Josse and C. Grimplet are acknowledged for technical assistance in microbial tests, and D. Harakat for recording mass spectra.

Keywords: Dolichandrone, Bignoniaceae, iridoids, phenylethanoid glycosides, antimicrobial.

References:

[1] Chandra Prasad PR, Reddy C, Redy SH, Dutt CBS. Folkore medicinal plants of North Andaman Island, India. Fitoterapia 2008; 79: 458 – 464

[2] Wiart C, Medicinal plants of the Asia-Pacific: Drugs for the future?, WSP Singapore; 2006: 566

[3] Godofredo USJr. Dolichandrone spathacea (Linn. F.) K. Schum. Available at http://www.stuartxchange.org/Tiwi.html. Accessed May 09, 2016

[4] Saiful AJ, Mastura M, Mazurah MI, Nuziah H. Inhibitory potential against methicillin-resistant Staphylococcus aureus (MRSA) of Dolichandrone spathacea, a mangrove tree species of Malaysia. Lat Am J Pharm 2011; 30: 359 – 362

[5] Rahalison L, Hamburger M, Hostettmann K, Monod M, Frenk E. A bioautography agar overlay method for detection of antifungal compounds from higher plants. Phytochemical Analysis 1991; 2: 199 – 203