Distribution, cytotoxicity, and antioxidant activity of fungal endophytes isolated from Tsuga chinensis (Franch.) Pritz. in Ha Giang province, Vietnam

Abstract

Purpose An endangered Tsuga chinensis (Franch.) Pritz. is widely used as a natural medicinal herb in many countries, but little has been reported on its culturable endophytic fungi capable of producing secondary metabolites applied in modern medicine and pharmacy. The present study aimed to evaluate the distribution of fungal endophytes and their cytotoxic and antioxidant properties. Methods This study used the surface sterilization method to isolate endophytic fungi which were then identified using morphological characteristics and ITS sequence analysis. The antimicrobial and cytotoxic potentials of fungal ethyl acetate extracts were evaluated by the minimum inhibitory concentration (MIC) and sulforhodamine B (SRB) assays, respectively. Paclitaxel-producing fungi were primarily screened using PCR-based molecular markers. Additionally, biochemical assays were used to reveal the antioxidant potencies of selected strains. Results A total of sixteen endophytic fungi that belonged to 7 known and 1 unknown genera were isolated from T. chinensis. The greatest number of endophytes was found in leaves (50%), followed by stems (31.3%) and roots (18.7%). Out of 16 fungal strains, 33.3% of fungal extracts showed significant antimicrobial activities against at least 4 pathogens with inhibition zones ranging from 11.0 ± 0.4 to 25.8 ± 0.6 mm. The most prominent cytotoxicity against A549 and MCF7 cell lines (IC50 value < 92.4 μg/mL) was observed in Penicillium sp. SDF4, Penicillium sp. SDF5, Aspergillus sp. SDF8, and Aspergillus sp. SDF17. Out of three key genes (dbat, bapt, ts) involved in paclitaxel biosynthesis, strains SDF4, SDF8, and SDF17 gave one or two positive hits, holding the potential for producing the billion-dollar anticancer drug paclitaxel. Furthermore, four bioactive strains also displayed remarkable and wide-range antioxidant activity against DPPH, hydroxyl radical, and superoxide anion, which was in relation to the high content of flavonoids and polyphenols detected. Conclusion The present study exploited for the first time fungal endophytes from T. chinensis as a promising source for the discovery of new bioactive compounds or leads for the new drug candidates.

Screening and characterization of paclitaxel-producing fungus \(\textit{Talaromyces wortmannii}\) WQF18 isolated from \(\textit{Cephalotaxus mannii }\)Hook. f..

“…The Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology supported for identification of C. mannii Hook. f. The collected bark was sterilized following the procedure previously described (Vu et al, 2022). In brief, the bark was treated with 70% ethanol for 30 s, 3.5% sodium hypochlorite solution for 2 min, 70% ethanol for 2-5 s, and rinsed with sterile distilled water.…”

“…Endophytic fungus Grammothele lineata recovered from the jute plant Corchorus olitorius was demonstrated to yield taxol (Das et al, 2017). A recent study reported four endophytic fungal strains from Tsuga chinensis that belonged to the genus Penicillium and Aspergillus held the potential of producing paclitaxel (Vu et al, 2022).…”

\(\textit{Fusarium fujikuroi}\) WQF5 isolated from \(\textit{Cephalotaxus mannii }\)Hook.f. as a producer of antibacterial agent and paclitaxel

“…Each culture was filtered by vacuum filtration and extracted twice with three volumes of ethyl acetate in a separatory funnel. After that, a solvent phase was concentrated and evaporated to dryness using a vacuum rotary evaporator at 45 o C (Vu et al, 2022). Each crude extract was weighed and dissolved in 1% (v/v) dimethyl sulfoxide (DMSO).…”

“…in Ha Giang province showed cytotoxicity on A549 and MCF7 cells, among them the most interesting strain Penicillium sp. SDF5 inhibited A549 and MCF7 cell lines with IC50 values of 14.2 ± 1.5 µg/mL and 25.2 ± 1.7 µg/mL, respectively (Vu et al, 2022). The United States National Cancer Institute Plant Screening Program claims that a crude extract has in vitro potent cytotoxicity if the IC50 value is lower than 30 μg/mL (Majoumouo et al, 2020), suggesting that the presence of bioactive compounds within WQF5 extract are potential for development as anticancer agents.…”

“…Endophytic fungi are known to colonize inside plant tissues without inflicting negative effects and even promote the ecological adaptability of their host under every environmental condition. Especially, fungal endophytes can mimic secondary metabolites from the host due to microbe-host interactions, which are an important source for the pharmaceutical industry (Zhou et al, 2007;Vu et al, 2022). The billion-dollar anticancer drug paclitaxel is widely used for the treatment of various cancers, which has only been extracted from the bark of Taxus species such as Taxus x media and Taxus baccata being listed in the International Union for Conservation of Nature (IUCN) Red List (Garyali et al, 2013).…”