Characterization and phytotoxicity of ophiobolins produced by <i>Bipolaris setariae</i>

Abstract

The Bipolaris setariae NY1 strain, isolated from a diseased green foxtail plant in Henan Province, China, showed strong pathogenicity towards green foxtail. In order to clarify the role of phytotoxic substances in the fungal pathogenicity, bioassay-directed isolation and bioactivity assays of secondary metabolites produced by the fungal strain were carried out. Five ophiobolins were obtained: 3-anhydro-ophiobolin A, 6-epi-ophiobolin A, 6-epi-ophiobolin B, 3-anhydro-6-epi-ophiobolin B and ophiobolin I. Bioassays on punctured and intact detached leaves of green foxtail indicated that 3-anhydro-ophiobolin A was the most phytotoxic, followed by 6-epi-ophiobolin A. The other three ophiobolins appeared to be inactive against green foxtail. The effects of 3-anhydro-ophiobolin A and 6-epi-ophiobolin A were synergistic. The symptoms on green foxtail caused by 3-anhydro-ophiobolin A or its mixture with 6-epi-ophiobolin A resembled those caused by the fungus. 3-Anhydro-ophiobolin A and 6-epi-ophiobolin A are likely the main pathogenic determinants of B. setariae. 6-epi-Ophiobolin A caused cytotoxicity against five kinds of human cancer cells: human colon adenocarcinoma cells (HCT-8), human liver cancer cells (Bel-7402), human gastric cancer cells (BGC-823), human lung adenocarcinoma cells (A549), and human ovarian adenocarcinoma cells (A2780). The results provide information for the development of herbicides and antitumor potential of the ophiobolin sesterterpenes.

LC–MS/MS-Guided Molecular Networking for Targeted Discovery of Undescribed and Bioactive Ophiobolins from Bipolaris eleusines

“…Zhao et al reported that 3-anhydroophiobolin A and 6-epi-ophiobolin A showed strong phytotoxicity on green foxtails whereas 6-epi-ophiobolin B and 3-anhydro-6-epi-ophiobolin B appeared to be almost inactive. 14 These data revealed that the C-ring formed by C-14 and C-17 contributed to their phytotoxicity. Sugawara et al reported four new ophiobolins with 7-CH 2 OH, which showed the potential phytotoxicity for the rice leaves, indicating that 7-CH 2 OH might be an active group.…”

“…Then, Fr.2 (11.0 g) was fractionated on a silica gel column using a petroleum ether−acetone (100:1−1:1) gradient to give three fractions (Fr. 13 C NMR (125 MHz, CDCl 3 ), Tables 1 and 3 13 C NMR (125 MHz, CDCl 3 ), Tables 1 and 3 13 C NMR (125 MHz, CDCl 3 ), Tables 1 and 3 13 C NMR (125 MHz, CDCl 3 ), Tables 1 and 3 Bipolaricin O (6): [α]25 D + 69.0 (c 0.1, MeOH); UV (MeOH) λ max (log ε) 210 (3.44) nm; IR (neat) ν max 2962, 1740, 1698, 1228, and 1026 cm −1 ; 1 H NMR (500 MHz, CDCl 3 ) and 13 C NMR (125 MHz, CDCl 3 ), Tables 1 and 3 13 C NMR (150 MHz, CDCl 3 ), Tables 2 and 4 (14), monoclinic, a = 16.8737(6) Å, b = 6.3485(3) Å, c = 21.0188(7) Å, U = 2077.43(14) Å 3 , T = 116.70 (14), α = 90.00°, β = 112.683(4)°, γ = 90.00°, space group I2 (no. 5), Z = 4, μ(Cu Kα) = 0.554, F(000) = 808, crystal size 0.35 × 0.08 × 0.03 mm 3 , 8792 reflections measured, 3521 unique (R int = 0.0340), which were used in all calculations.…”

“…This class of sesterterpenoids displayed a wide array of biological activities such as cytotoxicity, antimicrobial activity, and decreasing photosynthetic CO 2 fixation. − Yet, ophiobolins were first isolated as secondary phytotoxic metabolites from different pathogenic fungi of several crops (maize, rice, and sorghum), which ever led to two significant plant epidemic diseases in India (1943) and USA (1972) . In the recent years, with an increased consciousness of environmental protection, the ophiobolins were considered for further development as natural herbicides. − …”

Furanoids from the Gymnadenia conopsea (Orchidaceae) seed germination supporting fungus Ceratobasidium sp. (GS2)

“…All experiments were repeated at least three times. The effects were recorded after 3 days of observation ( Zhao et al, 2021 ).…”

Therapeutic vulnerabilities of cancer stem cells and effects of natural products

“…255 There are nearly 60 identied congeners of ophiobolins and studies predominantly focus on their bactericidal, fungicidal, nematocidal, and anti-calmodulin effects. [256][257][258][259][260][261] Fig. 6 shows representative members with key structural variations involving the C3, C14, and C21 oxidation states, C6 stereochemistry, and whether a D (tetrahydrofuran) ring is present.…”