A New Source of Diterpene Lactones From Andrographis paniculata (Burm. f.) Nees—Two Endophytic Fungi of Colletotrichum sp. With Antibacterial and Antioxidant Activities

Abstract

Endophytic fungi of medicinal plants are abundant, and their metabolites often have antioxidant, antibacterial, and antitumor effects and can produce secondary metabolites identical or similar to those of their hosts, which can mitigate the problem of insufficient supply of medicinal plants. In this study, we screened endophytic fungi for strains that produce the same diterpene lactones as Andrographis paniculata based on their biological activity. Firstly, the dominant group of endophytic fungi of Andrographis paniculata was screened and pathogenicity was studied using Koch’s rule. Secondly, DPPH, ABTS, OH, PTIO radical scavenging, and FRAP assays were used to detect the antioxidant activity of the extracellular extracts of the strains, and total phenol and total flavonoid contents of the strains with high antioxidant capacity were determined. S. aureus, B. subtilis, E. coli, and P. aeruginosa were used to determine the antibacterial activity of the mycelial extracts of the strains. Finally, the secondary metabolites of the mycelial extracts of the strains were examined by high-performance liquid chromatography. The results showed that 32 strains of Andrographis paniculata were relatively isolated > 70% and non-pathogenic. Extracellular extracts of strains AP-1 and AP-4 showed vigorous antioxidant activity, and AP-4, AP-12, AP-47, and AP-48 showed antibacterial activity against four strains of bacteria. The HPLC results indicated that the mycelial extracts of AP-4 and AP-12 contained diterpene lactones. The two endophytic fungi were recognized as Colletotrichum sp. The study successfully obtained diterpene lactones from the endophytic fungus of Andrographis paniculata and confirmed the feasibility of using endophytic fungal strains to produce active substances consistent with the host. It was also useful for exploring endophytic fungi and medicinal plants. The relationship provides theoretical guidance.

Endophytic fungus Colletotrichum sp. AP12 promotes growth physiology and andrographolide biosynthesis in Andrographis paniculata (Burm. f.) Nees

“…paniculata growth and secondary metabolism. Li et al. (2022b) reported that ADCs were detectable only in the mycelial fraction of AP12, which is further proof that the mycelia contain more active substances, may be certain growth hormones or key enzyme genes etc.…”

“…These results indicate that AP12 can activate the antioxidant defense system of A . paniculata , improve the host’s tolerance to external stress ( Hanada et al., 2010 ; Li et al., 2022b ), and endow the AP species that interact with AP12 with excellent potential resistance, laying a foundation for the breeding of high-quality and high-resistance A . paniculata varieties.…”

“…paniculata , identified as Colletotrichum sp. AP12 ( Li et al., 2022b ), was shown to have a potent antioxidant capacity and antibacterial ability and produced ADCs in a rich medium. Nevertheless, the content of ADCs gradually decreased after repeated subculturing, and it was speculated that it was associated with symbiosis A .…”

Metabolites of endophytic fungi isolated from leaves of Bauhinia variegata exhibit antioxidant activity and agonist activity on peroxisome proliferator-activated receptors α, β/δ and γ

“…that were characterized as five isocoumarin derivatives and a phthalide, of which four showed cytotoxic activity. In another work, Li et al (2022) demonstrated that diterpene lactones obtained from Colletotrichum sp. showed strong antibacterial and also antioxidant activity.…”

Identification and application of an endophytic fungus Arcopilus aureus from Panax notoginseng against crop fungal disease

“…The SQGX-6 extract was adjusted to five different concentrations (60, 80, 100, 200, and 400 μg/mL) for the antioxidant activity assays: 2,2-Diphenyl-1-pyridinyl hydrazide (DPPH) radical scavenging activity, 3-Ethylbenzothiazoline-6-Sulfonic Acid Radical scavenging (ABTS) activity, and superoxide anion radical (O 2 − ) scavenging activity; ascorbic acid (VC) was used as a positive control ( Li et al., 2022a ; Wu et al., 2022 ). The equations used to evaluate the different scavenging activities are as follows:…”