Clements Tanya, Rautenbach Marina, Ndlovu Thando, Khan Sehaam, Khan Wesaal
Department of Microbiology, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa.
BioPep™ Peptide Group, Department of Biochemistry, Faculty of Science, Stellenbosch University, Stellenbosch, South Africa.
Front Chem. 2021 Mar 16;9:633870. doi: 10.3389/fchem.2021.633870. eCollection 2021.
An integrated approach that combines reverse-phase high-performance liquid chromatography (RP-HPLC), electrospray ionization mass spectrometry, untargeted ultra-performance liquid chromatography coupled to tandem mass spectrometry (UPLC-MS) and molecular networking (using the Global Natural Products Social molecular network platform) was used to elucidate the metabolic profiles and chemical structures of the secondary metabolites produced by pigmented (P1) and non-pigmented (NP1) () strains. Tandem mass spectrometry-based molecular networking guided the structural elucidation of 18 compounds for the P1 strain (including 6 serratamolides, 10 glucosamine derivatives, prodigiosin and serratiochelin A) and 15 compounds for the NP1 strain (including 8 serratamolides, 6 glucosamine derivatives and serratiochelin A) using the MS fragmentation profiles. The serratamolide homologues were comprised of a peptide moiety of two L-serine residues (cyclic or open-ring) linked to two fatty acid chains (lengths of C, C, or C). Moreover, the putative structure of a novel open-ring serratamolide homologue was described. The glucosamine derivative homologues (i.e., -butylglucosamine ester derivatives) consisted of four residues, including glucose/hexose, valine, a fatty acid chain (lengths of C - C and varying from saturated to unsaturated) and butyric acid. The putative structures of seven novel glucosamine derivative homologues and one glucosamine derivative congener (containing an oxo-hexanoic acid residue instead of a butyric acid residue) were described. Moreover, seven fractions collected during RP-HPLC, with major molecular ions corresponding to prodigiosin, serratamolides (A, B, and C), and glucosamine derivatives (A, C, and E), displayed antimicrobial activity against a clinical S1 strain using the disc diffusion assay. The minimum inhibitory and bactericidal concentration assays however, revealed that prodigiosin exhibited the greatest antimicrobial potency, followed by glucosamine derivative A and then the serratamolides (A, B, and C). These results provide crucial insight into the secondary metabolic profiles of pigmented and non-pigmented strains and confirms that strains are a promising natural source of novel antimicrobial metabolites.
采用一种综合方法，该方法结合了反相高效液相色谱（RP-HPLC）、电喷雾电离质谱、非靶向超高效液相色谱-串联质谱（UPLC-MS）和分子网络（使用全球天然产物社会分子网络平台），以阐明色素沉着（P1）和无色素（NP1）（）菌株产生的次生代谢产物的代谢谱和化学结构。基于串联质谱的分子网络利用质谱裂解图谱指导了对P1菌株18种化合物（包括6种serratamolides、10种葡糖胺衍生物、灵菌红素和serratochelin A）和NP1菌株15种化合物（包括8种serratamolides、6种葡糖胺衍生物和serratochelin A）的结构解析。serratamolide同系物由两个L-丝氨酸残基（环状或开环）的肽部分与两条脂肪酸链（C、C或C长度）相连组成。此外，还描述了一种新型开环serratamolide同系物的推定结构。葡糖胺衍生物同系物（即丁基葡糖胺酯衍生物）由四个残基组成，包括葡萄糖/己糖、缬氨酸、一条脂肪酸链（C - C长度，从饱和到不饱和不等）和丁酸。描述了七种新型葡糖胺衍生物同系物和一种葡糖胺衍生物同系物（含有氧代己酸残基而非丁酸残基）的推定结构。此外，在RP-HPLC过程中收集的七个馏分，其主要分子离子对应于灵菌红素、serratamolides（A、B和C）和葡糖胺衍生物（A、C和E），使用纸片扩散法对临床S1菌株显示出抗菌活性。然而，最低抑菌和杀菌浓度测定表明，灵菌红素表现出最大的抗菌效力，其次是葡糖胺衍生物A，然后是serratamolides（A、B和C）。这些结果为色素沉着和无色素菌株的次生代谢谱提供了关键见解，并证实菌株是新型抗菌代谢产物的有前途的天然来源。
