Isolation of two diterpenoids from mangrove plant Rhizophora mangle by countercurrent chromatography

Mangrove plants are potential sources of biologically active compounds what is revealed by their numerous traditional and medicinal uses [1]. Of Brazil's 7408 km coastline, 6786 km contain mangrove forests, covering 25.000 km². Rhizophora mangle (Rhiphoraceae), known as red mangrove, is a Brazilian native tree and occurs in all Brazilian mangrove areas [2]. The plant is used for the extration of tannins, which make 15 – 36% of the dry bark [3]. Phytochemical studies on the species reported the isolation of flavonoids, tanins and triterpenes from the leaves [4]. In this work two labdane diterpenes, manool and jhanol (Figure 1), were isolated from the hexane extract of aerial roots by countercurrent chromatography using a biphasic non-aqueous solvent system composed of hexane-acetonitrile-methanol 1:1:0.5 (v/v/v).

The literature reports the presence of kaurane, labdane, pimarane and beyerane diterpenes in Rhizophoraceae family [4], but not manool and jhanol specifically. Labdane diterpenes have several biological activities such as antibacterial, antifungal and antiprotozoal properties [3]. These structures will serve as starting point for semi-synthesis of pharmacologically active compounds.

Fig. 1: Isolated diterpenes (1) manool and (2) jhanol

References:

[1] Bandaranayake WM. Mangroves and Salt Marshes 2 (1998) 133 – 148.

[2] Schaeffer-Novelli Y. Aquatic Ecosystem Health and Management 2000; 3: 561.

[3] Chapman VJ. Mangrove phytosociology. Tropical Ecology 1970; 11: 1.

[4] Nebula M et al. Natural Products and Bioprospecting 2013; 3: 207.