Antimicrobial Studies of the Transition Metal Complexes of the African Black Soap from Elaeis guineensis (Palm Kernel Oil) and Theobroma cacao (Cocoa)

African black soap is an indigenous organic soap formed by saponification. Its laboratory-controlled
preparation was carried out by reacting palm kernel oil and the filtrate of cocoa pod ash. The
elucidation of its ability to act as a ligand was carried out after its reaction with some transition
metal salts which were Cu(CH3COO)2.H2O, Pb(CH3COO)2.3H2O and FeCl3. The metal:ligand
ratio (M:L) was 3:1. These reactions were carried out in an aqueous medium to give the
corresponding complexes [Pb(C11H23COO-K+)2(C11H23COO-)2].9H2O, [Cu(BL)4(C11H23COO-)2].4H2O
and [Fe(BL)2(C11H23COO-)Cl2] with the percentage yield of 56, 48 and 41%, respectively.
Characterization of the prepared compounds was done by spectroscopic and physicochemical
analyses. Physicochemical analyses of the black soap revealed the moisture content was 26% (w/w),
total fatty matter (TFM) was 44.75% (w/w), total fatty alkaline (TFA) was 0.22% (w/w), total alkaline
(TA) was 11.78% (w/w) and pH was 10. The solubility of the metal complexes determined at room
temperature in various solvents revealed it increased as polarity decreased. Spectra analyses
corroborate an octahedral structure for the Pb(II), a distorted octahedral structure for the Cu(II) and an
octahedral Fe(III) complex, in which African black soap (C11H23COO-K+) has acted either as a
monodentate or bidentate ligand. The in-vitro antimicrobial activities of these compounds evaluated
against two gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis), two gram-negative
bacteria (Escherichia coli and Pseudomonas aeruginosa) and two fungi (Aspergillus species and
Rhizopus species) revealed that complex [Cu(BL)4(C11H23COO-)2].4H2O was active against
Staphylococcus aureus and Rhizopus species, while all other compounds remained inactive against
the tested compounds.