New α-glucosidase inhibiting anthracenone from the barks of Harungana madagascariensis Lam

Two new 10-hydroxy-9(10H)-anthracenone, madagascenone A (1) and B (2), were isolated from the barks of Harungana madagascariensis Lam. The structures of the compounds were determined using 1D- and 2D-NMR and mass spectroscopic techniques. Both of the compounds showed an in vitro α-glucosidase inhibition with IC₅₀ = 69.9 ± 4.21 and 122.3 ± 1.13 μM, respectively, more potent than the standard acarbose (IC₅₀ = 840 ± 1.23 μM).     

Chemical composition of the essential oil of Kaliphora madagascariensis Hook. f.

Kaliphora madagascariensis is an evergreen shrub or small tree endemic to Madagascar where it is traditionally used for the treatment of persistent cephalalgia by a strong inhalation of its odour. In this work, we analysed for the first time the essential oil obtained from leaves by Gas Chromatography-Mass Spectrometry. The chemical composition was dominated by oxygenated sesquiterpenes (68.1%), with caryophyllene oxide (14.7%) and β-eudesmol (10.7%) as the most abundant constituents. These compounds are endowed with documented healthy effects such as analgesic, anti-inflammatory, neuritogenic, antiepileptic and hypotensive, and its abundance might explain the traditional use of the plant in Madagascar.     

Structures of cadinane- and guaiane-type sesquiterpenoids from Enterospermum madagascariensis (Baill.) Homolle

Three new cadinane- and guaiane-type sesquiterpenoids, 2-hydroxy-10-epi-zonarene 1, 2, 15-dihydroxycalamenene 2 and guaia-4, 6-dien-3-one 3, were isolated from the wood of Enterospermum madagascariensis (Rubiaceae) grown in Madagascar. Their structures were established from concerted application of 2D NMR techniques including gs-COSY, gs-HMQC, gs-HMBC and NOESY.