Antifungal Activity on the Strain of Lasiodiplodia theobromae and Phytochemical Study of Ageratum conyzoides and Newbouldia laevis from the Kisangani Region / DR Congo

Abstract

Aims: To extract, identify and evaluate in vitro the antifungal activity of the phytochemical groups of Ageratum conyzoides and Newbouldia laevis on the strain of Lasiodiplodia theobromae.
 Study Design: Exploitation of medicinal plants to combat the growth of L. theobromae, responsible for the decline of cocoa cultivation.
 Location and Duration of Studies: Faculty of Sciences, University of Kisangani, between April 2017 and February 2018.
 Methodology: The crude extracts of the dry leaves of A. conyzoides and N. laevis were tested (at 100 mg/mL). Potato dextrose agar was used as the culture medium. After chemical screening, abundant phytochemical groups were isolated and tested.
 Results: The aqueous, 95% ethanolic and ethereal crude extracts of A. conyzoides are more antifungal (respective percentages of inhibition PI: 80.74; 84.10 and 85.64%) than those of N. laevis (63.28; 72.64 and 75.23%). The minimum inhibitory concentration (MIC) of the aqueous crude extract of A. conyzoides is lower (25 mg/mL) than that of the ethanolic extract (50 mg/mL). Tannins are very abundant in A. conyzoides and in N. laevis. Saponins, sterols and terpenes are abundant in both plants. The extraction yields of tannins and saponins are respectively 20.67 and 2.43% in A. conyzoides and 10.47 and 2.38% in N. laevis. A. conyzoides contains the gallic tannins while N. laevis, the condensates and catechics. The saponins and tannins of A. conyzoides are more antifungal (respective PI: 84.40 and 54.44%) than those of N. laevis (PI: 75.56 and 32.96%).
 Discussion: The saponins of A. conyzoides and N. laevis are more active on the strain of L. theobromae than the tannins. Saponins are surfactants that can destabilize membrane structure of microorganisms including fungi.
 Conclusion: The saponins of the two plants have shown a very interesting antifungal power on the strain of L. theobromae. The identification of their active molecules is ongoing.

Chemical Composition of Essential Oil of Ageratum conyzoides with Antifungal Activity on the Lasiodiplodia theobromae Strain in the Region of Kisangani and DR Congo

“…Terpenes and Sterols are very abundant in the leaves of A. conyzoides. These secondary metabolites were also identified by N'guessan, [40], thus confirming our previous results [14]. However, these results are contrary to those of Bouquet and Debray [41].…”

“…The essential oil of the leaves of A. conyzoides has a slightly higher PI (P= 4.187e -05 ) than that of its saponins (84.44%) [14]. It showed antifungal activity on the strain of L. theobromae, like the essential oils of Ocimum gratissimum, Ocimum canum, and Syzygium aromaticum which have a very pronounced activity on the strains of toxigenic molds isolated from peanuts [23,58].…”

“…In 1985, Lasiodiplodia theobromae was identified as a phytopathogenic fungus responsible for this brown rot [6,7]. Other studies had revealed the presence of this germ on cocoa in South America, Ecuador, India, Western Samoa, the Philippines [8][9][10] and recently in the Kisangani region in the Democratic Republic of the Congo, DRC [11][12][13][14]. This endophyte can cause tree death [15].…”

“…Several studies have been carried out to highlight its antimicrobial activities [28,29]. And recently in our series of studies on plants with antifungal activity on the strain of L. theobromae, the non-volatile extracts of A. conyzoides were tested [12,14].…”

Evaluation of Toxicity of Some Tropical Flora, Clay and Permethrin against Sitophilus zeamais Motsch. on Stored Maize Grains

“…Ageratum conyzoides and Cymbopogon citratus are commonly used herbs for treating boils and malaria in Trado-Medicare (Soujanya et al, 2016;Enyiukwu et al, 2021). Studies showed that C. citratus and A. conyzoides inhibited Alternaria bataticola and Botrydiplodia theobromae (Kwembe et al, 2020;Enyiukwu et al, 2021). In Africa, formulations of Hyptis suaveolus and Mangifera indica inhibited oviposition, while the progeny emergence of Prostephanus truncatum and S. zeamais can protect treated maize grains (90%) for 5 months (Ngamo et al, 2007;Gariba et al, 2021).…”