Diversity and communities of culturable endophytic fungi from the root holoparasite Balanophora polyandra Griff. and their antibacterial and antioxidant activities

Abstract

Purpose: Balanophora polyandra Griff. is a holoparasitic medicinal plant that produces compounds with antibacterial and antioxidant activities. Plant endophytic fungi are an abundant reservoir of bioactive metabolites for medicinal exploitation, and an increasing number of novel bioactive compounds are being isolated from endophytic fungi. The present study investigated the diversity of culturable endophytic fungi from the roots of holoparasite B. polyandra to explore active strains and metabolites. In addition, the antibacterial and antioxidant activities of 22 strains cultured from B. polyandra were also evaluated. Methods: The endophytic fungi were identified according to their colony morphology and ITS-5.8S rDNA sequencing. TLC-MTT-Bioautography assays and DPPH radical scavenging assays were employed to assess the antibacterial and antioxidant activities of ethyl acetate extracts of the endophytic fungi. Results: One hundred and twenty-five endophytic strains were isolated from the roots of B. polyandra, including 70 from female samples and 55 from male samples. Of them, twenty-two distinct isolates representing 15 genera and 22 species based on their ITS-rDNA genomic sequence were successfully identified from female and male samples of B. polyandra. The genus Calonectria was the most prevalent genus, with a CF% of 18.3, followed by the genera Clonostachys and Botryosphaeria, with CF% values of 13.4 and 10.0, respectively. Interestingly, the fungal extracts exhibited broad-spectrum antibacterial activities against gram-positive and gram-negative bacteria, as well as potential antioxidant activities with IC50 values ranging from 0.45 to 6.90 mg/mL. Among them, endophytes Bpf-10 (Diaporthe sp.) and Bpf-11 (Botryosphaeria sp.) showed the strongest biological activities and more abundant secondary metabolites. Conclusions: This study reported the diversity of endophytic fungi from the roots of B. polyandra and the antibacterial and antioxidant activities of the crude extracts for the first time. The results revealed that B. polyandra contains diverse culturable endophytic fungi that potentially produce natural antibacterial and antioxidant compounds with great value to the agriculture and pharmaceutical industries.