Anti-plasmodial and Cholinesterase Inhibiting Activities of some Constituents of Psorospermum glaberrimum

Abstract

Malaria is still the most devastating parasitic disease in the world, causing 2-3 million deaths every year, mostly among children under five years old and pregnant women. Africa accounts for over 90% of malaria mortality. 1) In the last decades resistance of Plasmodium falciparum, the causative agent of the most severe form of the disease, to several antimalarials, especially chloroquine and antifolates, became widely disseminated, while the cost of effective treatment is prohibitive for the large majority of the populations. For these reasons, new effective and affordable antimalarials are urgently needed.2) In Africa and elsewhere, the use of indigenous plants plays an important role in malaria treatment. 3)These plants are indeed an interesting source of new antiplasmodial compounds perhaps with new mechanisms of action.Psorospermum glaberrimum HOCHR. (Hypericaceae) is a small-to medium-sized shrub (up to 3 m high) distributed in tropical regions. Leaves and bark extracts of this plant are used in traditional medicine for the treatment of several diseases across Africa.4) The decoctions of leaves and bark are used to treat epilepsy, respiratory affections and external uses for skin diseases and leprosy. The extracts of the root bark are used for the treatment of severe cases of malaria. The pulped roots and bark extracts and the bark red resin powdered with dried leaves are remedies used externally for skin diseases and leprosy. The boiled bark gives a soapy product that is mixed with oil to rub on the skin or applied to sores for animals to keep away flies that cause scabies.4) Previous phytochemical investigations of Psorospermum species reported the presence of bioactive xanthones, anthraquinones, vismiones and psorolactones.5-16) Although some phytochemical studies have been carried out on P. glaberrimum, to the best of our knowledge, no investigation has been reported on its anti-plasmodial activity and inhibitory properties towards acetyl-and butyrylcholinesterase (AChE and BChE). AChE and BChE have been identified as attractive targets in the treatment of Alzheimer's dementia, myasthenia gravis, glaucoma, and in the recovery of victims of nerve agent exposure. Any chemical that inhibits cholinesterase activity increases the availability of acetylcholine to sustain nerve cell communications.17) Hence, cholinesterase inhibitors act as potential leads in drug discovery for nervous-system disorders.In our continuing interest in new bioactive metabolites from Cameroonian medicinal plants, we investigated the hexane extract of stem bark of P. glaberrimum which showed potent anti-plasmodial activity against the W2 strain of P. falciparum, and good AChE and BChE inhibition in vitro. In this paper, we report on the isolation and structure elucidation of a new bianthrone derivative 1, the 13 C-NMR data of the known bianthrone A2b (11) together with the anti-plasmodial and cholinesterase inhibiting activities of the isolated compounds. Results and DiscussionThe air dried stem bark of P. glaberrimum was extracted...

The potential of anti-malarial compounds derived from African medicinal plants, part II: a pharmacological evaluation of non-alkaloids and non-terpenoids

“…[80]. These include glaberianthrone ( 56 ), 3-geranyloxyemodin anthrone ( 57 ), acetylvismione D ( 58 ), 2-geranylemodin ( 59 ), bianthrone 1a ( 60 ), and 3-prenyloxyemodin anthrone ( 61 ).…”

The potential of anti-malarial compounds derived from African medicinal plants. Part I: A pharmacological evaluation of alkaloids and terpenoids

“…The compound had an IC 50 of 2.05 μg mL -1 [116]. The n -hexane extract of Psorospermum glaberrimum from Cameroon showed good anti-plasmodial activity against the P. falciparum W2 strain, with IC 50 of 0.87 μg mL -1 [117]. Lenta et al .…”

A rule to distinguish diastereomeric bianthrones by 1H NMR

“…[1][2][3][4][5][6][7][8][9][10] They are also regarded as important intermediates in the biosyntheses of photosensory pigments with ingestion-deterrent, antiviral, and sedative properties, and some have been obtained as intermediates in the chemical syntheses of these pigments. 11,12 Additionally, the photochromic derivatives with a double bond between C-10 and C-10 0 have attracted much attention for molecular electronics, and they may be taken as potential structural elements in supramolecular assemblages due to the conductance-switching property.…”

“…1,8 The specic optical rotation ([a] D ) has once been used to identify them, but the possible impurity for mesomers or 1 : 1 ratio for enantiomers are neglected. 2,4,8 Additionally, the epimerization and photooxidation under acidic conditions preclude hydrolyses and derivations by some chemical methods. 6,16 Thus, the congurations for most of the substituted bianthrones have been assigned almost in chaos so far due to the meso, racemic, and axisrotating phenomena, which may restrict the application and development of these molecules to some extent.…”