Paclitaxel is possibly the most famous natural product of endophytic fungi. This highly functionalized diterpenoid is a potent antimitotic compound originally isolated from the stem bark of the western yew, Taxus brevifolia. It was the first natural substance that demonstrated antimycotic, antileukemic, and tumor inhibitory activities ^[1][164]. In 1993, the first endophytic fungi producing paclitaxel was reported. Taxomyces andreanae was isolated from the inner bark of T. brevifolia and produced paclitaxel and related compounds when grown in a semisolid synthetic medium ^[2][165]. Frequently, paclitaxel-producing endophytic fungi have been isolated from different sources other than Taxus trees, even at a higher concentrations than those isolated from Taxus trees; such is the case of studies focused on endophytes from plants used in traditional medicine ^[3][4][5][6][166,167,168,169]. For example, Cladosporium oxysporum, isolated from the medicinal plant Moringa oleifera yields 550 μg/L in liquid fermentation ^[7][170], a high concentration considering that Taxomyces andreanae yielded 0.05 μg/L at similar culture conditions. Likewise, Phoma betae from Ginkgo biloba leaves yielded 795 μg/L ^[5][168]. Now, hundreds of fungi isolated from yew and other plants have been shown to produce paclitaxel ^[8][171], including patents for the production of paclitaxel from endophytic fungi focused on optimization of the production process, methods for purification from the fermentation broth, and methods for screening paclitaxel-producing endophytic fungi ^[9][172].

Podophyllotoxin is an aryltetralin–lignan anticancer metabolite produced by several plants, mainly by Sinopodophyllum hexandrum; it is used in the East and Middle East as traditional medicine. Podophyllotoxin serves as a precursor to three key chemotherapeutic drugs: etoposide, teniposide, and etoposide phosphate ^[10][173]. Etoposide is widely used to treat various types of cancer and has recently been proposed as an adjunct treatment to immunosuppressants for critically ill COVID-19 patients ^[11][12][174,175]. Several endophytic fungi from different plant species have been reported to produce podophyllotoxin at different concentrations; likewise, two patents concerning methods for the identification of podophyllotoxin-producing fungi and production and recuperation processes of podophyllotoxin in liquid fermentation have been issued ^[9][172].

Vinca alkaloids (vincristine and vinblastine) and semisynthetic derivatives (vinorelbine, vindesine, and vinflunine) are remarkable antimitotic chemotherapeutics utilized in the treatment of hematological and lymphatic neoplasms. These indole terpenoids stop mitosis by inhibiting the formation of microtubules (at low concentration) or depolymerizing microtubules (at high concentrations) ^[13][176]. Some fungi produce vinblastine or vincristine under specific culture conditions, such as Botryosphaeria laricina CRS1, an endophyte of Catharanthus roseus, in which high yields of vinblastine and vincristine are dependent on elicitors present in extracts of the host plant ^[14][177]. In the case of Alternaria alternata and Talaromyces radius, the yield of vinblastine depends on media composition ^[15][16][178,179]. Despite the fact that Catharanthus roseus has many endophytic fungi, only some of them have been demonstrated to produce vinblastine or vincristine ^[17][18][180,181]. Other approaches include the use of endophytes to elicit the accumulation of Vinca alkaloids in the leaves of C. roseus. Inoculation of these plants with two of their endophytes (Curvularia sp. CATDLF5 and Choanephora infundibulifera CATDLF6) was found to enhance vindoline content by upregulating genes related to the terpenoid indole alkaloid biosynthesis in C. roseus ^[19][182]. Similar results were observed in cell suspension cultures of the same plant ^[20][183].

Together with paclitaxel and Vinca alkaloids, camptothecin (including its analogs) belongs to the most important chemotherapeutic drugs. Camptothecin is an indole-terpene alkaloid extracted from the bark of Camptotheca acuminata ^[21][184], used as the precursor of two more potent camptothecin analogs: topotecan, and irinotecan. Different from the previously described substances, which are antimitotic drugs, camptothecins belong to the group of topoisomerase inhibitors, particularly camptothecins that act by inhibiting DNA topoisomerase I, an enzyme found in significantly high levels in many cancer surgical specimens ^[13][22][176,185]. Commercially, camptothecin is extracted from C. acuminata and Nothapodytes nimmoniana with yields up to 0.3% of dry weight ^[23][186]. Most endophytic camptothecin-producing fungi have been isolated from those host plants (Table 6). Aspergillus niger, Alternaria alternata, and Fusarium solani were isolated from Piper betle, Miquelia dentata, and Apodytes dimidiata, respectively ^[24][25][26][187,188,189]. The highest yield was obtained from Trichoderma atroviride LY357, isolated from C. acuminata, about 197.82 µg/L ^[27][190]. Despite the high yield among endophytic fungi, it is little exploited in industry ^[28][191].

Fusidic acid is an antibiotic isolated in 1962 from the fermentation broth of a strain of Fusidium coccineum ^[29][192]. Chemically, it is a fusidane triterpenoid inhibitor of prokaryotic elongation factor (EF-G), hence it stops protein synthesis ^[30][193]. This antibiotic is particularly important in infections by staphylococci, including the methicillin-resistant Staphylococcus aureus (MRSA) ^[31][194]. Recently, the endophytic fungus Acremonium pilosum F47 has been reported to produce authentic fusidic acid, two known analogs (16-desacetylfusidic acid and 3β,20-dihydroxy-protosta-16,24-dien-29-oic acid), and a new derivative, acremonidiol A. ^[32][195]. A few more fungi, such as Sarocladium oryzae, an endophyte of Oryza rufipogon Griff. (Dongxiang wild rice) ^[33][196], and Xylaria sp., endophyte of Anoectochilus setaceus ^[34][197], have been shown to produce other fusidane-type antibiotics, including helvolic acid.

Secondary Metabolite	Representative Endophytic Fungi	References
Paclitaxel (anticancer chemotherapy drug)	Aspergillus candidus, Chaetomella raphigera, Cladosporium cladosporioides, Cladosporium oxysporum, Lasiodiplodia theobromae, Penicillium aurantiogriseum, Periconia sp., Pestalotiopsis microspora, Pestalotiopsis versicolor, Phoma betae, Phomopsis sp., Phomopsis sp., Phomopsis sp., Phyllosticta citricarpa, Phyllosticta melochiae	[5][6][7][35][36][37][38][39][40][41][42][43][44]	[168,169,170,198,199,200,201,202,203,204,205,206,207]
Camptothecin and analogs (anticancer chemotherapy drug)	Fusarium solani, Fusarium oxysporum, Entrophospora infrequens, Trichoderma atroviride, Neurospora sp., Alternaria alstroemeriae, Alternaria burnsii, Alternaria sp., Alternaria alternata, Xylaria sp., Aspergillus sp., Aspergillus niger	[24][25][26][27][45][46][47][48][49][50][51][52]	[187,188,189,190,208,209,210,211,212,213,214,215]
Vinblastine and vincristine (anticancer chemotherapy drug)	Alternaria alternata	sp,	Fusarium oxysporum	,	Talaromyces radicus	,	Curvularia verruculosa	,	Botryosphaeria laricina	[14][15][16][53][54]	[177,178,179,216,217]
Podophyllotoxin (anticancer chemotherapy)	Phialocephala fortinii (0.5 to 189 μg/L), Alternaria tenuissima, Mucor fragilis, Trametes hirsuta, Alternaria sp. Fusarium solani	[55][56][57][58][59][60]	[218,219,220,221,222,223]
Fusidic acid (antibiotic)	Acremonium pilosum	[32]	[195]