African black soap or black soap, also known as Alata Samina or Alata originated from West Africa (Bella, 2008). It has being used since ancient time in Ghana and Nigeria, where it also enjoys several names like Ose Dudu, Eko Zhiko and Sabulon Salo (Getradeghana, 2000). This  indigenous African organic soap is formed by esterification (Bella, 2008). It has found a wide application for all household cleaning purposes from bathing to washing and cleaning (Getradeghana, 2000). Black soap enjoys a good reputation for its ability to deeply cleanse the skin’s pores, remove blemishes and makeup, improve or eliminate uneven skin tone, razor bumps caused by ingrown hairs and skin rashes (Getradeghana, 2000). It is not scented and therefore can be used by anyone who wishes to improve the quality of his/her skin (Getradeghana, 2000). We have previously reported the preparation of African black soap by reacting palm kernel oil and the filtrate of burnt cocoa pods (the ash). The chemical analyses of the black soap revealed 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 (Ikotun et al., 2017a). Some metal complexes were thereafter prepared by the reaction of the prepared black soap with some transition metal salts. The characterization of the black soap and prepared complexes done by spectroscopic analyses and determination of physicochemical properties revealed that the potassium salt (C₁₁H₂₃COO^-K⁺), commonly called African black soap, acted either as a monodentate or bidentate ligand forming metal complexes by coordinating through one or two of its oxygen donor atoms and also by entirely replacing the potassium ion with the transition metal (displacement reaction). Our interest in this indigenous African black soap has previously led to studies using the ash from the sun dried cocoa pods (Ikotun et al., 2017b). This present work was aimed at preparing African black soap using the waste material from cocoa (cocoa pod burnt to ash without prior sun drying) and palm kernel oil. Thereafter, the different portions of the prepared black soap were enhanced with some naturally occurring beautifying organic compounds and analyzed chemically. Also, phytochemical analysis and in-vitro antimicrobial studies were carried out on them. This literature therefore serves as the first report on the physicochemical analyses, phytochemical analyses and antimicrobial studies of burnt cocoa pod filtrate prepared African black soap, as well as that of its enhanced samples with some skin-nourishing natural products.

 

Chemical

Palm kernel seeds and cocoa pods were locally sourced from a town called Ifeodan, Osun State, Nigeria. All solvents used were purchased    as      analytical     grades    from    Sigma-Aldrich   and SAARChem

Instrumentation

The Infrared spectra were recorded as KBR plates on a Nicolet Avatar FTIR 330 spectrophotometer. Hanna Professional Waterproof pH/ORP meter was used for determining the pH.

Preparation of the black soap

African Black soap was prepared according to literature (Ikotun et al., 2017b) and divided into five portions. Some beauty enhancing natural compounds were added as additives into four of the soap portions in separate labeled containers, followed by manual pounding with a pestle and mortar. Part A was without additives, while part B contained 12.50 g of black soap pounded with half table spoon of squeezed aloe vera. Sample C contained 12.50 g of black soap pounded with 0.7 g cam wood. Sample D contained 12.50 g black soap pounded with 7 drops of lime. Part E was enhanced by pounding 12.50 g black soap with 0.35 g shea butter and 0.35 g camwood. These samples were analyzed by pH determinations, infrared spectroscopic analyses and phytochemical screenings.

Antimicrobial test

15.2 g of Mueller Hinton agar was measured into a 500-ml conical flask, 400 ml of distilled water was added and mixed/shaken till it dissolved, it was then covered with cotton wool and aluminum foil paper and labeled. It was autoclaved at a temperature of 121°C for 15 min. The agar was allowed to cool to a temperature of 45°C and aseptically poured into sterile Petri dishes. The poured agar was allowed to solidify. 0.5 g of the prepared samples and 2.5 ml of distilled water were dispensed into Mac Cartney bottles and allowed to dissolve. Sterile filter paper disc (7 mm in diameter) was then placed inside the dissolved soap mixture and allowed to soak for 10 min. The plates were then inoculated with the test bacteria using the spread plate method with a sterile swab stick. The test bacteria were two Gram-positive bacteria (Staphylococcus aureus and Bacillus subtilis) and two Gram-negative bacteria (Pseudomonas aeruginosa and Escherichia coli) (Cheesbrough, 2002; Emeruwa, 1982). The inoculated plates were kept on the work bench for 1 h before further work was carried out. The soaked discs were picked using forceps sterilized by flaming and placed aseptically on the inoculated Petri dishes. The discs were allowed to stick on to the surface of the agar medium before incubation. The plates were incubated at 37°C for 24 h and antibacterial activity of the soap was measured as diameter of zones of inhibition surrounding the impregnated filter paper discs. Zones of inhibition were measured in mm (Bauer et al., 1996; Balogun and Owoseni, 2013).

 

 

 

Dunn (2011) reported the equation for the preparation of black soap as Equation 1, while Figure 1 presents its structure (Ikotun et al., 2017b).

 

 

Sample A , black soap alone; sample B, black soap with aloe vera; sample C, black soap with camwood; sample D, black soap with lime; sample E, black soap with sheabutter and camwood.

pH determinations

Table 1 presents the pH values of the black soap and its enhanced samples. The pH determinations showed that all the samples were alkaline in nature with values between 8.7 and 9.1. Tarun et al. (2014) stated that majority of soaps have a pH value between 9 and 10.

 

 

FTIR spectra analyses

The FTIR spectra of the African black soap (Figure 2) and its enhanced samples (Figures 3 to 6) have been analyzed and presented as Table 2. The characteristic vibrational frequencies have been identified by comparing the spectra of the prepared African black soap with the enhanced samples (Ikotun et al., 2017a). The broad medium band at 3381 cm^-1 in sample A was assigned to the stretching vibration of OH. This band shifted to a lower frequency of 3374 cm^-1 in samples B and E, while appearing at 3376 cm^-1 in C and at 3364 cm^-1 in D. The spectrum of A showed  the sp³ C-H  stretching  vibrations at 2920, 2957 and 2863 cm^-1, respectively. These bands have also appeared at about the same frequencies in all its enhanced samples. The stretching vibrational frequency of C=O for sample A appeared as a medium and a strong band at 1740 and 1562 cm^-1. These bands have appeared unchanged in all other samples. The stretching vibrational frequency of C-O of sample A was assigned the value 1119 cm^-1. The band appeared unchanged in samples B and C, but shifts to a slightly lower frequency at 1117 cm^-1 in samples D and E. This analysis shows that the structure of black soap is intact and it was not denatured by the various additives.

 

 

 

 

 

Phytochemical screenings

The results of the phytochemical screenings of all the black soap samples are presented below as Table 3. The results showed that samples A and D contained saponin, while all the samples contained terpenoids. Sample C contained flavonoids, while tannins and steroids are absent in all the samples. These results revealed the presence of some essential secondary metabolites which nourish the skin.

 

 

Antimicrobial screenings

The results of the antibacterial activities of the black soap and its enhanced samples are displayed in Figure 7. Sample B, which contained aloe vera, was active against both Gram-positive bacteria, as well as E. coli. Sample C, which contained camwood, was active against S. aureus and E. coli. Sample D, which contained lime, was active against both Gram-negative bacteria and the only one active against P. aeruginosa. It was also active against S. aureus. Sample E, which contained shea butter and camwood, was only active against the B. subtillis. African black soap remained inactive against all tested microorganisms.

 

 

 

 

 

 

The results of the phytochemical screenings of black soap revealed it contains some secondary metabolites which are nourishing to the skin. This is a good justification for the reason it cleanses deeply and nourishes all skin types. The enhancement of black soap with some other natural skin beautifying compounds did not affect or denature it, but rather facilitated its antimicrobial activities.

 

The authors have not declared any conflict of interests.