Page 21 - 7-Windhoek MORNING SESSION e-BOOK (27 April 2023)

School of Science
FACULTY OF AGRICULTURE,
ENGINEERING & NATURAL SCIENCES

DOCTOR OF PHILOSOPHY IN SCIENCE
(MEDICINAL CHEMISTRY)

CANDIDATE: NYAMBE Moola M

CANDIDATE’S DISSERTATION
ANTI-GONOCOCCAL ACTIVITY OF EXTRACTS
FROM SELECTED NAMIBIAN MEDICINAL
PLANTS AND COMPUTATIONAL STUDIES OF
XERANTHOLIDE, A NEISSERIA GONORRHOEAE
INHIBITO.

The doctoral study was undertaken and completed under the
supervision of Professor Kazhila C. Chinsembu (Main-Supervisor) and
Prof. Edet F. Archibong (Co-Supervisor) of the University of Namibia.

The candidate studied thirteen plant species that are traditionally
used to treat gonorrhea in Namibia. She reported on plant extracts
that inhibit the activity of Neisseria gonorrhoeae, the causative agent
of gonorrhea, thus validating the traditional use of some of the plants.
The seminal findings of the study include the isolation of two pure
compounds (xerantholide and hiptagin) from two different plant
species. Xerantholide, a sesquiterpene lactone, was determined to
be the active anti-gonorrheal ingredient of the the plant Pechuel-
loeschea leubnitziae. In search of other biologically active compounds,
in-silico study of 83 other sesquiterpene lactones which are analogues
of xerantholide was done. The study of the interaction of xerantholide
and its analogues with Neisseria gonorrhoeae carbonic anhydrase
(NgCA), an essential enzyme in the life of the bacterium, revealed
the potential of these compounds as NgCA inhibitors. The interaction
mode with the active site of NgCA was revealed to be through various
bond types such as hydrogen bond, metal-acceptor interaction
through (Zn2+), alkyl interaction, and pi-alkyl interactions, thus making
the ligand-receptor complex stable.
This mode of action is significant because it is different from the
mode of action used by existing gonorrhea drugs. The results of this
research, already published in revered international journals, open
a new pipeline in the discovery of novel anti-gonorrheal drugs from
indigenous Namibian medicinal plants.

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