LC-MS/MS Tandem Mass Spectrometry for Analysis of Phenolic Compounds and Pentacyclic Triterpenes in Antifungal Extracts of Terminalia brownii (Fresen).

Enass Y A Salih,Mustafa K M Fahmi,Hiba A Ali,Marketta Sipi,Pia Fyhrquist,Olavi Luukkanen,Markku Kanninen,Ashraf M A Abdalla,Abdelazim Y Abdelgadir,Mai H Elamin

doi:10.3390/antibiotics6040037

Abstract

Decoctions and macerations of the stem bark and wood of Terminalia brownii Fresen. are used in traditional medicine for fungal infections and as fungicides on field crops and in traditional granaries in Sudan. In addition, T. brownii water extracts are commonly used as sprays for protecting wooden houses and furniture. Therefore, using agar disc diffusion and macrodilution methods, eight extracts of various polarities from the stem wood and bark were screened for their growth-inhibitory effects against filamentous fungi commonly causing fruit, vegetable, grain and wood decay, as well as infections in the immunocompromised host. Ethyl acetate extracts of the stem wood and bark gave the best antifungal activities, with MIC values of 250 µg/mL against Nattrassia mangiferae and Fusarium verticillioides, and 500 µg/mL against Aspergillus niger and Aspergillus flavus. Aqueous extracts gave almost as potent effects as the ethyl acetate extracts against the Aspergillus and Fusarium strains, and were slightly more active than the ethyl acetate extracts against Nattrassia mangiferae. Thin layer chromatography, RP-HPLC-DAD and tandem mass spectrometry (LC-MS/MS), were employed to identify the chemical constituents in the ethyl acetate fractions of the stem bark and wood. The stem bark and wood were found to have a similar qualitative composition of polyphenols and triterpenoids, but differed quantitatively from each other. The stilbene derivatives, cis- (3) and trans- resveratrol-3-O-β-galloylglucoside (4), were identified for the first time in T. brownii. Moreover, methyl-(S)-flavogallonate (5), quercetin-7-β-O-di-glucoside (8), quercetin-7-O-galloyl-glucoside (10), naringenin-4′-methoxy-7-pyranoside (7), 5,6-dihydroxy-3′,4′,7-tri-methoxy flavone (12), gallagic acid dilactone (terminalin) (6), a corilagin derivative (9) and two oleanane type triterpenoids (1) and (2) were characterized. The flavonoids, a corilagin derivative and terminalin, have not been identified before in T. brownii. We reported earlier on the occurrence of methyl-S-flavogallonate and its isomer in the roots of T. brownii, but this is the first report on their occurrence in the stem wood as well. Our results justify the traditional uses of macerations and decoctions of T. brownii stem wood and bark for crop and wood protection and demonstrate that standardized extracts could have uses for the eco-friendly control of plant pathogenic fungi in African agroforestry systems. Likewise, our results justify the traditional uses of these preparations for the treatment of skin infections caused by filamentous fungi.

Highlights

Fungal contamination is both a pre- and a post-harvesting problem in crop production and poses a continuous and growing threat to global food crop production [1,2]
Extracts, the ethyl acetate extracts of the stem wood and bark gave the highest antifungal activity. This result is in accordance with other authors, who reported that especially ethyl acetate extracts
We found that the obtained values correlated well with the sizes the sizes of the inhibition zones produced by these ethyl acetate extracts, so that small MIC valuesof were inhibition these ethyl acetate soTo that were coupled to coupled tozones large produced diameters by of the inhibition zonesextracts, (Table 1)

Summary

Introduction

Fungal contamination is both a pre- and a post-harvesting problem in crop production and poses a continuous and growing threat to global food crop production [1,2]. Especially A. flavus, and A. niger cause aspergillosis in immunocompromised individuals [9,10]. Nattrassia mangiferae is a human pathogenic fungus, especially in immunocompromised individuals [15], and is even known to cause community acquired infections in rural farmer societies worldwide [13]. Fusarium verticilloides and some other Fusarium species infect maize ears (husks) causing maize ear rot disease and contaminate maize grains with fumonisin mycotoxins leading to major pre- and post-harvest losses [16]. Fusarium spp. mycotoxins are toxic [17,18], and fumonisin has been found to cause cancer in mammalians [19] Another species of Fusarium, F. oxysporum is the causative agent of the “Panama disease” affecting the banana (Musa paradisiaca), the staple food of a large part of Africa

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