Fusarisolins A–E, Polyketides from the Marine-Derived Fungus Fusarium solani H918

Five new (fusarisolins A–E, 1 to 5) and three known (6 to 8) polyketides were isolated from the marine-derived fungus Fusarium solani H918, along with six known phenolics (9 to 14). Their structures were established by comprehensive spectroscopic data analyses, methoxyphenylacetic acid (MPA) method, chemical conversion, and by comparison with data reported in the literature. Compounds 1 and 2 are the first two naturally occurring 21 carbons polyketides featuring a rare β- and γ-lactone unit, respectively. All isolates (1 to 14) were evaluated for their inhibitory effects against tea pathogenic fungus Pestalotiopsis theae and 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) synthase gene expression. Compound 8 showed potent antifungal activity with an ED50 value of 55 μM, while 1, 8, 13, and 14 significantly inhibited HMG-CoA synthase gene expression.

As part of our continuing discovery for structurally novel and biologically interesting secondary metabolites from marine microorganisms [17][18][19][20], the fungal strain Fusarium solani H918, isolated from mangrove sediments, was selected for a systematical chemical investigation due to its significant inhibitory activity against tea pathogenic fungus Pestalotiopsis theae. Extensive chromatographic separation of the EtOAc extract of the fermented cultures resulted in the isolation of eight polyketides (1 to 8) and six phenolic compounds (9 to 14) (Figure 1), of which compounds 1 and 2 are novel and 2 are novel polyketides featuring a rare β-and γ-lactone ring, respectively. Herein, we report the isolation, structural elucidation, and bioactivities of these compounds.

Results and Discussion
Compound 1 was isolated as a colorless oil. The protonated molecular ion peak at m/z 367.2446 [M + H] + (calcd for C 21 H 35 O 5 , 367.2426) in the high resolution electron spray ionization mass spectrum (HRESIMS) indicated its molecular formula as C 21 H 34 O 5 , requiring five degrees of unsaturation. The infrared absorption (IR) absorption at 1818 cm −1 indicated the presence of a β-lactone moiety. Its 1 H NMR spectrum showed two signals as doublets (δ H 0.87 and 1.04) and two as singlets (δ H 1.82 and 2.20) assigned to the four methyl groups, one hydroxymethyl (δ H 3.77, 3.91), two olefinic protons (δ H 5.65 and 5.76), and one oxymethine (δ H 4.31) (Table 1), while the 13 C NMR spectrum exhibited 21 carbon resonance signals, including four methyls, seven methylenes, six methines (two olefinics), and four nonprotonated sp 2 carbons (two carbonyls) ( Table 2). Among them, four olefinic carbons (δ C 119.1, 130.6, 142.2, and 155.2) for two double bonds and two ester carbonyl carbons (δ C 171.0 and 172.1) accounted for four indices of hydrogen deficiency. The remaining one degree of unsaturation was due to the presence of a monocyclic ring in the molecule, which was consistent with the presence of a β-lactone ring as indicated by the IR spectrum. Analyses of the heteronuclear single quantum correlations (HSQC), 1 H-1 H correlated spectroscopy (COSY), and heteronuclear multiple bond correlations (HMBC) spectra of 1 determined a 1,2-dialkylated β-lactone skeleton, structurally close the coexisted antibiotics 1233A (8) [2]. The COSY cross-peaks of H-14 (δ H 4.31)/H-15 (δ H 3.53)/H 2 -21 (δ H 3.91, 3.77) and the HMBC interactions from H 2 -21 to C-14 (δ C 80.2), C-15 (δ C 58.2), and C-16 (δ C 172.1) and from H 3 -18 (δ H 1.04) to C-12 (δ C 32.4)/C-13 (δ C 38.1)/C-14 revealed a hydroxymethyl and a alkyl chain to be attached to C-15 and C-14 positions, respectively ( Figure 2). The alkyl chain was expanded from C-12 to C-1 (δ C 171.0) as evidenced by the contiguous COSY cross-peaks from H 2 -6 (δ H 2. 13 Figure 2. On the basis of the above data, the alkyl side chain with 13 carbons bearing four methyl groups was elucidated as a 3,5,7-trimethyl-tetradeca-2,4-dienoic acid. Therefore, the gross structure of 1 was determined as a novel 21 carbons polyketide featuring a rare β-lactone moiety.  Figure 2. On the basis of the above data, the alkyl side chain with 13 carbons bearing four methyl groups was elucidated as a 3,5,7-trimethyl-tetradeca-2,4dienoic acid. Therefore, the gross structure of 1 was determined as a novel 21 carbons polyketide featuring a rare β-lactone moiety.  [11,21]. The same orientation of H-13 and H-15 was presumed by the NOESY cross-peaks from H-15 to H-13 and H3-20 ( Figure 2). Absolute configuration of C-15 was determined by application of the MPA method used for establishing absolute configuration and optical purity of primary alcohols with chiral center at C-2 position [22,23]. The chemical shift difference between two methylene protons of H2-21 in (R)-MPA ester (1a) (∆δH 0.08) is larger than that of (S)-MPA ester (1b) (∆δH 0.05), revealing 15R configuration. Additionally, the absolute configuration of C-7 at linear side chain was presumed to be the same as that of 8 according to the biogenetic considerations, which was based on the fact that the isolate 8 was established as 1233A by comparison of their NMR data and specific rotation values between 8 ([α] 25 D 25.6, CHCl3) and 1233A ([α] 25 D 27.5, CHCl3) [2,24]. Therefore, the structure of 1 was then established as a novel (2E,4E,7R,13R)-13-((2R,3R)-3-(hydroxymethyl)-4-oxooxetan-2-yl)-3,5,7-trimethyltetradeca-2,4-dienoic acid, and given the name, fusarisolin A. Compound 2 exhibited the same molecular formula as that of 1 according to its HRESIMS spectrum. Interestingly, it also showed nearly identical 13 C NMR data to those of 1 revealing a structurally similar analogue. The difference was attributed to the methine of C-13 and oxymethine of C-14 of 1 being replaced by an oxygenated nonprotonated sp 3 carbon (δC 86.5) and methylene (δC 36.5), respectively, suggesting the presence of a γ-lactone instead of a β-lactone unit in 2. This assumption was evidenced by the HMBC correlations from H3-20 (δH 1.    Figure 2. On the basis of the above data, the alkyl side chain with 13 carbons bearing four methyl groups was elucidated as a 3,5,7-trimethyl-tetradeca-2,4dienoic acid. Therefore, the gross structure of 1 was determined as a novel 21 carbons polyketide featuring a rare β-lactone moiety.  [11,21]. The same orientation of H-13 and H-15 was presumed by the NOESY cross-peaks from H-15 to H-13 and H3-20 ( Figure 2). Absolute configuration of C-15 was determined by application of the MPA method used for establishing absolute configuration and optical purity of primary alcohols with chiral center at C-2 position [22,23]. The chemical shift difference between two methylene protons of H2-21 in (R)-MPA ester (1a) (∆δH 0.08) is larger than that of (S)-MPA ester (1b) (∆δH 0.05), revealing 15R configuration. Additionally, the absolute configuration of C-7 at linear side chain was presumed to be the same as that of 8 according to the biogenetic considerations, which was based on the fact that the isolate 8 was established as 1233A by comparison of their NMR data and specific rotation values between 8 ([α] 25 D 25.6, CHCl3) and 1233A ([α] 25 D 27.5, CHCl3) [2,24]. Therefore, the structure of 1 was then established as a novel (2E,4E,7R,13R)-13-((2R,3R)-3-(hydroxymethyl)-4-oxooxetan-2-yl)-3,5,7-trimethyltetradeca-2,4-dienoic acid, and given the name, fusarisolin A. Compound 2 exhibited the same molecular formula as that of 1 according to its HRESIMS spectrum. Interestingly, it also showed nearly identical 13 C NMR data to those of 1 revealing a structurally similar analogue. The difference was attributed to the methine of C-13 and oxymethine of C-14 of 1 being replaced by an oxygenated nonprotonated sp 3 carbon (δC 86.5) and methylene (δC 36.5), respectively, suggesting the presence of a γ-lactone instead of a β-lactone unit in 2. This assumption was evidenced by the HMBC correlations from H3-20 (δH 1.   Figure 2. On the basis of the above data, the alkyl side chain with 13 carbons bearing four methyl groups was elucidated as a 3,5,7-trimethyl-tetradeca-2,4dienoic acid. Therefore, the gross structure of 1 was determined as a novel 21 carbons polyketide featuring a rare β-lactone moiety.  [11,21]. The same orientation of H-13 and H-15 was presumed by the NOESY cross-peaks from H-15 to H-13 and H3-20 ( Figure 2). Absolute configuration of C-15 was determined by application of the MPA method used for establishing absolute configuration and optical purity of primary alcohols with chiral center at C-2 position [22,23]. The chemical shift difference between two methylene protons of H2-21 in (R)-MPA ester (1a) (∆δH 0.08) is larger than that of (S)-MPA ester (1b) (∆δH 0.05), revealing 15R configuration. Additionally, the absolute configuration of C-7 at linear side chain was presumed to be the same as that of 8 according to the biogenetic considerations, which was based on the fact that the isolate 8 was established as 1233A by comparison of their NMR data and specific rotation values between 8 ([α] 25 D 25.6, CHCl3) and 1233A ([α] 25 D 27.5, CHCl3) [2,24]. Therefore, the structure of 1 was then established as a novel (2E,4E,7R,13R)-13-((2R,3R)-3-(hydroxymethyl)-4-oxooxetan-2-yl)-3,5,7-trimethyltetradeca-2,4-dienoic acid, and given the name, fusarisolin A. Compound 2 exhibited the same molecular formula as that of 1 according to its HRESIMS spectrum. Interestingly, it also showed nearly identical 13 C NMR data to those of 1 revealing a structurally similar analogue. The difference was attributed to the methine of C-13 and oxymethine of C-14 of 1 being replaced by an oxygenated nonprotonated sp 3 carbon (δC 86.5) and methylene (δC 36.5), respectively, suggesting the presence of a γ-lactone instead of a β-lactone unit in 2.   Figure 2. On the basis of the above data, the alkyl side chain with 13 carbons bearing four methyl groups was elucidated as a 3,5,7-trimethyl-tetradeca-2,4dienoic acid. Therefore, the gross structure of 1 was determined as a novel 21 carbons polyketide featuring a rare β-lactone moiety.  [11,21]. The same orientation of H-13 and H-15 was presumed by the NOESY cross-peaks from H-15 to H-13 and H3-20 ( Figure 2). Absolute configuration of C-15 was determined by application of the MPA method used for establishing absolute configuration and optical purity of primary alcohols with chiral center at C-2 position [22,23]. The chemical shift difference between two methylene protons of H2-21 in (R)-MPA ester (1a) (∆δH 0.08) is larger than that of (S)-MPA ester (1b) (∆δH 0.05), revealing 15R configuration. Additionally, the absolute configuration of C-7 at linear side chain was presumed to be the same as that of 8 according to the biogenetic considerations, which was based on the fact that the isolate 8 was established as 1233A by comparison of their NMR data and specific rotation values between 8 ([α] 25 D 25.6, CHCl3) and 1233A ([α] 25 D 27.5, CHCl3) [2,24]. Therefore, the structure of 1 was then established as a novel (2E,4E,7R,13R)-13-((2R,3R)-3-(hydroxymethyl)-4-oxooxetan-2-yl)-3,5,7-trimethyltetradeca-2,4-dienoic acid, and given the name, fusarisolin A. Compound 2 exhibited the same molecular formula as that of 1 according to its HRESIMS spectrum. Interestingly, it also showed nearly identical 13 C NMR data to those of 1 revealing a structurally similar analogue. The difference was attributed to the methine of C-13 and oxymethine of C-14 of 1 being replaced by an oxygenated nonprotonated sp 3 carbon (δC 86.5) and methylene (δC 36.5), respectively, suggesting the presence of a γ-lactone instead of a β-lactone unit in 2.  [11,21]. The same orientation of H-13 and H-15 was presumed by the NOESY cross-peaks from H-15 to H-13 and H 3 -20 ( Figure 2). Absolute configuration of C-15 was determined by application of the MPA method used for establishing absolute configuration and optical purity of primary alcohols with chiral center at C-2 position [22,23]. The chemical shift difference between two methylene protons of H 2 -21 in (R)-MPA ester (1a) (∆δ H 0.08) is larger than that of (S)-MPA ester (1b) (∆δ H 0.05), revealing 15R configuration. Additionally, the absolute configuration of C-7 at linear side chain was presumed to be the same as that of 8 according to the biogenetic considerations, which was based on the fact that the isolate 8 was established as 1233A by comparison of their NMR data and specific rotation values between 8 ([α] 25 D 25.6, CHCl 3 ) and 1233A ([α] 25 D 27.5, CHCl 3 ) [2,24]. Therefore, the structure of 1 was then established as a novel (2E,4E,7R,13R)-13-((2R,3R)-3-(hydroxymethyl)-4-oxooxetan-2-yl)-3,5,7-trimethyltetradeca-2,4-dienoic acid, and given the name, fusarisolin A.
Compound 4 showed the same molecular formula as that of 3 by the HRESIMS spectrum and their NMR spectroscopic data were nearly identical, indicating a structurally related analogue. Comparison of the NMR data, as well as the analyses of 2D NMR spectra (HSQC, COSY, and HMBC), established the structure of 4 to be a 2Z isomer of 3. This assumption was recognized by the shielded chemical shifts of H 3 -1 (∆δ H −0.17), the deshielded shift of Me-15 (∆δ C +7.2), in association with the NOESY relationships from H-2 (δ H 5.30) to H 3 -15 (δ H 1.70) and from H-4 (δ H 5.53) to H 2 -6 (δ H 2.09, 1.86). The 2Z and 4E configuration of the double bond at ∆ 2 and ∆ 4 of 4 were unambiguously determined by the clear NOESY data, which further supported the 2E and 4E configurational assignments of 3. Accordingly, the structure of 4 was established as (2Z)-fusarisolin C, and named fusarisolin D.  25 D +10.1) [28], the sole stereogenic center of C-7 was assigned as S configuration. Consequently, the structure of 5 was established as (2E,5E,7S)-8-methoxy-3,5,7-trimethyl-8-oxoocta-2,5-dienoic acid, and named fusarisolin E.
Compound 6 exhibited the molecular formula of C 19 H 32 O 6 as established by the HRESIMS spectrum of the sodium adduct ion peak (m/z 379.2094). The NMR data were nearly identical to those of 7 except for the presence of additional methoxyl signals (δ H 3.71, δ C 52.0). The location of methoxyl group at C-14 (δ C 175.1) was corroborated by the HMBC interaction from the methoxyl protons (δ H 3.71) to the carbonyl carbon of C-14. The NOESY cross-peaks from H 2 -6 (δ H 1.89, 2.14) to H-4 (δ H 5.76) and from H-4 to H-2 (δ H 5.65) revealed the 2E and 4E configurations of the conjugated double bonds. Therefore, the structure of 6 was elucidated as 14-O-methyl-12-epi-1233B. Although 6 is commercially available, no physicochemical data could be found. Accordingly, its 1 H and 13 C NMR data (Tables 1 and 2) are reported here for the first time.
In order to establish the absolute configuration of C-12 in 7, compound 8 (1233A) was subjected to alkaline hydrolysis to provide 7 (Figure 4). According to the identical 1 H-and 13 C-NMR spectra and specific rotation data between hydrolysis product of 8 ( Figure S8-1 and 8-2), 7 was concluded to have the opposite configuration at C-12 to that of 1233B, establishing 7 to be 12-epi-1233B [2]. Considering the absence of the 13 C NMR spectroscopic data of 12-epi-1233B in the literature, the modern 1 H-and 13 C-NMR data of 7 are provided in Table S1 of the Supplementary Materials.  [28], the sole stereogenic center of C-7 was assigned as S configuration. Consequently, the structure of 5 was established as (2E,5E,7S)-8methoxy-3,5,7-trimethyl-8-oxoocta-2,5-dienoic acid, and named fusarisolin E.
Compound 6 exhibited the molecular formula of C19H32O6 as established by the HRESIMS spectrum of the sodium adduct ion peak (m/z 379.2094). The NMR data were nearly identical to those of 7 except for the presence of additional methoxyl signals (δH 3.71, δC 52.0). The location of methoxyl group at C-14 (δC 175.1) was corroborated by the HMBC interaction from the methoxyl protons (δH 3.71) to the carbonyl carbon of C-14. The NOESY cross-peaks from H2-6 (δH 1.89, 2.14) to H-4 (δH 5.76) and from H-4 to H-2 (δH 5.65) revealed the 2E and 4E configurations of the conjugated double bonds. Therefore, the structure of 6 was elucidated as 14-O-methyl-12-epi-1233B. Although 6 is commercially available, no physicochemical data could be found. Accordingly, its 1 H and 13 C NMR data (Tables 1  and 2) are reported here for the first time.
Compounds 1 to 14 were evaluated for antifungal activities against tea pathogenic fungus Pestalotiopsis theae. Only compound 8 exhibited a potent effect with an ED 50 value of 55 ± 4.0 µM, which was stronger than that of the positive control hexaconazole (ED 50 = 68 ± 5.7 µM). Previously, 1233A (8) was reported to be a specific inhibitor of HMG-CoA synthase [3]. However, currently there is no commercially available Pestalotiopsis theae HMG-CoA synthase enzyme. It is known that synthase gene expression is positively correlated to synthase expression, i.e., the down/up regulation of gene expression leads to the lower/higher expression of protein. Therefore, all isolates were tested for the down-regulation of Pestalotiopsis theae HMG-CoA synthase gene expression by real-time polymerase chain reaction (RT-PCR) at the concentration of 10 µM, and abscisic acid and dimethyl sulfoxide (DMSO) were used as positive and blank controls [36]. As a result, compounds 1, 8, 13, and 14 Mar. Drugs 2019, 17, 125 7 of 12 showed a significant effect, while 2, 4, 10, and 11 exhibited a moderate effect, and 12 showed a weak effect ( Figure 5). As in the case of 8, compounds 1, 13, and 14 might also have potent inhibitory activity against HMG-CoA synthase, revealing their potential applications in regard to control of cholesterol biosynthesis. Dimethyl sulfoxide (DMSO) and abscisic acid were used as blank and positive controls, respectively. G lyceraldehyde-3-phosphate dehydrogenase (GAPDH) was used as reference gene. Values represent the mean ± SD of three independent experiments. * p < 0.05, ** p < 0.01, and *** p < 0.001.

General Experimental Procedures
Optical rotations were recorded on a Rudolph Autopol IV automatic polarimeter under 24 °C (Rudolph Research Analytical, Hackettstown, NJ, USA). The IR spectrum was recorded on a Bruker IFS-55 spectrometer (Bruker Optik BmbH, Ettlingen, Germany). The HRESIMS spectra were measured by a Waters Xevo G2 Q-TOF mass spectrometer (Waters, Milford, MA, USA). The NMR spectra were recorded on a Bruker Avance-400 FT MHz NMR spectrometer (Bruker, Fällanden, Switzerland). High performance liquid chromatography (HPLC) was carried out on an Alltech instrument equipped with UV detector (Series III, Alletch Inc., Nicholasville, Kentucky, USA). Thinlayer chromatography (TLC) analysis was performed on precoated silica gel plates (Jiangyou Silica Gel Development, Inc., Yantai, China). Column chromatography (CC) was performed on Sephadex LH-20, ODS, and silica gel, respectively.

Fungal Identification, Fermentation, and Extract
The fungus Fusarium solani H918 was isolated from mangrove sediments collected at the Zhangjiangkou Mangrove National Nature Reserve, Fujian, China. The internal transcribed spaces (ITS) region was amplified and sequenced by the general primers ITS1 and ITS4. The ITS region of the fungus was 576 bp DNA sequence (GenBank accession number: KY978584), which showed 99% identity to Fusarium solani. The strain was deposited at the China Center for Type Culture Collection (CCTCC) with the accession number of M 2017151.
Prior to the large-scale fermentation, the producing strain was incubated on a potato dextrose agar (PDA) plate medium under 25 °C for 3 days, and then the fresh mycelia were inoculated to 25 ×

General Experimental Procedures
Optical rotations were recorded on a Rudolph Autopol IV automatic polarimeter under 24 • C (Rudolph Research Analytical, Hackettstown, NJ, USA). The IR spectrum was recorded on a Bruker IFS-55 spectrometer (Bruker Optik BmbH, Ettlingen, Germany). The HRESIMS spectra were measured by a Waters Xevo G2 Q-TOF mass spectrometer (Waters, Milford, MA, USA). The NMR spectra were recorded on a Bruker Avance-400 FT MHz NMR spectrometer (Bruker, Fällanden, Switzerland). High performance liquid chromatography (HPLC) was carried out on an Alltech instrument equipped with UV detector (Series III, Alletch Inc., Nicholasville, Kentucky, USA). Thin-layer chromatography (TLC) analysis was performed on precoated silica gel plates (Jiangyou Silica Gel Development, Inc., Yantai, China). Column chromatography (CC) was performed on Sephadex LH-20, ODS, and silica gel, respectively.

Fungal Identification, Fermentation, and Extract
The fungus Fusarium solani H918 was isolated from mangrove sediments collected at the Zhangjiangkou Mangrove National Nature Reserve, Fujian, China. The internal transcribed spaces (ITS) region was amplified and sequenced by the general primers ITS1 and ITS4. The ITS region of the fungus was 576 bp DNA sequence (GenBank accession number: KY978584), which showed 99% Prior to the large-scale fermentation, the producing strain was incubated on a potato dextrose agar (PDA) plate medium under 25 • C for 3 days, and then the fresh mycelia were inoculated to 25 × 1 L Erlenmeyer flasks, each containing 80 g of rice and 120 mL of sea water. The fermentation was carried out under static conditions at 25 • C for 20 days. Following this, fermented cultures were extracted with EtOAc three times and concentrated under reduced pressure to get an organic extract. The extract was re-dissolved in MeOH and extracted with petroleum ether (PE) three times. The MeOH layer was evaporated under reduced pressure to get a defatted extract (6 g).

Isolation and Purification
The

Alkaline Hydrolysis of 8
A tetrahydrofuran (THF) solution (100 µL) of 8 (5.0 mg, 0.015 mmol) was mixed with NaOH (2.5 mg, 0.0625 mmol) and H 2 O (400 µL). This reaction mixture was left at room temperature for 2 h, and then the pH value was adjusted to 3-4 with hydrochloric acid (1 M). After being extracted with CHCl 3 three times, the extract was subjected to CC over ODS eluting with MeOH/H 2 O (7:3) to yield 7 (3.0 mg).

Antifungal Assay
Antifungal assay against tea pathogenic fungus Pestalotiopsis theae HQ832793, isolated from foliar lesions of tea leaf, was performed in PDA Petri plates according to a previously described method [37]. In brief, a 0.6 cm diameter piece of tested fungal strains cylinder agar was placed on the center, and sterile blank paper discs (0.5 cm diameter) were placed at a distance of 2 cm away from the growing mycelial colony. The tested compounds (100 µg/mL, DMSO solution) were added to each paper disc. DMSO and hexaconazole were used as blank and positive controls, respectively. These plates were incubated at 28 • C until mycelial growth enveloped the discs including the control disc. The experiment was repeated three times.

ED 50 Detection
As reported previously [38], different concentrations of the DMSO dissolved 1233A and hexaconazole were mixed with a PDA medium and poured into a set of PDA Petri plates. The Pestalotiopsis theae mycelial disk (5 mm) was placed in the center of each treated Petri dish and incubated at 28 • C. All treatments were quadruplicated against each fungus. DMSO and hexaconazole were used as blank and positive controls, respectively. The ED 50 value was calculated statistically by Probit analysis.

Total RNA Isolation
Pestalotiopsis theae cells were cultured in a PDA medium for 3 days at 28 • C, then treated with tested compounds for 16 h. Cells were harvested by centrifugation at 6000 rpm for 5 min, and then homogenized in liquid nitrogen. Total RNA was extracted with Spin Column Fungal Total RNA Purification Kit (Sangon Biotech, Shanghai, China).

RT-PCR Analysis of HMG-CoA Synthase Gene Expression
The inhibitory effects of the tested compounds at 10 µM (DMSO dissolution) on the mRNA expression of HMG-CoA synthase in Pestalotiopsis theae cells were analyzed by RT-PCR. DMSO and abscisic acid (10 µM) were used as blank and positive controls, respectively. The expression of mRNA transcripts of HMG-CoA synthase (forward: TACTCG CTCACCTGCTACAC; reverse: GCGTACGACTTCTGGACGAC) and GAPDH (forward: CATGTCCATGCGTGTCCCTA; reverse: CAGTGGAGACAACCTCGTCC) was determined by RT-PCR. The cDNA was synthesized from total RNA using PrimeScript RT reagent kit with gDNA Eraser (Takara, Japan). TaKaRa SYBR ® Premix Ex Taq™ II (Takara, Japan) and Stepone Real-Time PCR Detection System (Applied Biosystems, Foster City, CA, USA) were used for RT-PCR analysis. The values are expressed as the mean ± SD for three triplicate experiments.

Conclusions
The present work reported five new (1 to 5) and nine known (6 to 14) compounds from the marine-derived fungus Fusarium solani H918. Fusarisolins A (1) and B (2), two novel 21-carbon polyketides featuring a rare βand γ-lactone unit, respectively, were found for the first time in nature . Compounds 1, 8, 13, and 14 showed significant down-regulation HMG-CoA synthase gene expression. In addition, compound 8 exhibited potent inhibitory activity against tea pathogenic fungus Pestalotiopsis theae, revealing that it might be a potential lead compound for the development of an antifungal agrochemical after structural modification.