title: Ultraviolet-visible study on acid-base equilibria of aporphine alkaloids with antiplasmodial and antioxidant activities from Alseodaphne corneri and Dehaasia longipedicellata.
abstract: The UV-vis spectra of isocorydine 1, norisocorydine 2 and boldine 3 were studied in 2% v/v acetonitrile, at constant ionic strength (0.1 M NaCl, 35 degree Celsius). The pK(a) values of isocorydine 1 and norisocorydine 2 were 11.75 and 12.07, respectively. Boldine 3 gave a pK(a) value of 9.16 and 10.44. All of the alkaloids 1-3 were stable at physiological pH; thereby all of them will not ionize, thus permitting the basic nitrogen to be protonated and accumulated within the acidic food vacuole of Plasmodium via pH trapping. Subsequently, acidic food vacuoles that have been neutralized by alkaloids would result in enhancement of the antiplasmodial activity. The alkaloids showed antiplasmodial activity against Plasmodium falciparum and antioxidant activities; DPPH radical scavenging, metal chelating and ferric reducing power. The antioxidant properties of the alkaloids under investigation revealed that in addition to the antiplasmodial activity, the alkaloids can also prevent oxidative damage. It can be prevented by binding free heme and neutralizing the electrons produced during the Plasmodium falciparum mediated haemoglobin destruction in the host. Slightly basic properties of the aforementioned alkaloids, along with their antioxidant activities, are advantageous in improving the suppression of malaria infection that cause less damage to the host.
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Azeana
authors.initials: A
authors.lastname: Zahari
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Abdulwali
authors.initials: A
authors.lastname: Ablat
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Noridayu
authors.initials: N
authors.lastname: Omer
authors.affiliation: Chemistry Department, Faculty of Science and Mathematics, University of Pendidikan Sultan Idris, 35900 Tanjung Malim, Perak, Malaysia.
authors.forename: Mohd Azlan
authors.initials: MA
authors.lastname: Nafiah
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Yasodha
authors.initials: Y
authors.lastname: Sivasothy
authors.affiliation: Institute of Biological Sciences, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Jamaludin
authors.initials: J
authors.lastname: Mohamad
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Mohammad Niyaz
authors.initials: MN
authors.lastname: Khan
authors.affiliation: Department of Chemistry, Faculty of Science, University of Malaya, 50603 Kuala Lumpur, Malaysia.
authors.forename: Khalijah
authors.initials: K
authors.lastname: Awang
mesh_terms: D000470:Alkaloids / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000962:Antimalarials / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology*; D000975:Antioxidants / Q000737:chemistry / Q000302:isolation & purification / Q000494:pharmacology; D001060:Aporphines / Q000737:chemistry / Q000494:pharmacology; D006801:Humans; D019770:Lauraceae / Q000737:chemistry; D008288:Malaria / Q000188:drug therapy* / Q000469:parasitology / Q000473:pathology; D015394:Molecular Structure; D010936:Plant Extracts / Q000737:chemistry / Q000494:pharmacology*; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000472:pathogenicity
chemical_list: D000470:Alkaloids; D000962:Antimalarials; D000975:Antioxidants; D001060:Aporphines; D010936:Plant Extracts; C081279:aporphine; C030168:isocorydine; C011686:boldine