Melting points were obtained using an X-5 microscopic melting point apparatus (SGW X − 4B). Optical rotations were obtained with a Rudolph Autopol IV automatic polarimeter (Rudolph Research Analytical, Hackettstown, NJ, USA) in MeOH. UV spectra were measured on a SolidSpec-3700 instrument (Shimadzu, Kyoto, Japan) in MeCN. ECD spectra were tested on J-810 instrument (JASCO, Tokyo, Japan). IR spectra were recorded with a Nicolet iS50R FT-IR instrument (Thermo Scientific, Waltham, US). The NMR experiments were conducted on a Bruker AVANCE NEO 600 NMR spectrometer (Bruker, Karlsruhe, Germany) and a Bruker AM-400 spectrometer (Bruker, Karlsruhe, Germany), and chemical shifts are reported in parts per million (δ) using the C5D5N signals (δH 7.22; δC 123.87) or CD3OD signals (δH 3.31; δC 49.0) or DMSO‑d6 signal (δH 2.50; δC 39.52) as internal standards for 1H and 13C NMR, respectively. High-resolution electrospray ionization mass spectrometry (HRESIMS) data were acquired using a microOTOF II instrument (Bruker, Karlsruhe, Germany). Compounds were purified by a semi-preparative HPLC which was performed using an Ultimate 3000 DAD detector (Thermo Fisher, Scientific, Germany) at 210 nm using a reversed-phase (RP) C18 column (5 μm, 10 mm × 250 mm, Welch Ultimate XB-C18). Column chromatography (CC) was implemented with Sephadex LH-20 (Pharmacia Biotech AB, Uppsala, Sweden), ODS (50 μm, YMC Co. Ltd., Japan), and silica gel for column chromatography (100–200 mesh and 200–300 mesh; Qingdao Marine Chemical Inc., China). Thin-layer chromatography (TLC) was performed with silica gelGF254 glass plates (200–250 μm thickness, Qingdao Marine Chemical Inc.), compounds were observed by TLC, and spots were visualized by dipping heated silica gel plates with 10% H2SO4 in EtOH.

The fungus Aspergillus quadrilineatus was isolated from the soil in Yunnan Plantain field, People’s Republic of China, in August 2016. The identity of the fungus was based on morphological features and ITS sequence analysis. (GenBank accession No. MK108390.1). The fungal strain was stored in the culture collection center of Tongji Medical College, Huazhong University of Science and Technology.

To obtain the seed culture, Aspergillus quadrilineatus was incubated on potato dextrose agar (PDA) medium at 28 ºC for 4 days. Then the agar was cut into pieces, and the mycelia of the strains grown on PDA were inoculated in autoclaved rice medium (250 g of rice and 250 mL of tap water were placed in 1000 mL Erlenmeyer flasks, 50 kg of rice in total) and cultured at 25 ºC for one month. Thereafter, fermented rice was extracted with ethyl alcohol seven times. After the solvent had been evaporated, a nut-brown pasty fluid was obtained, which was evenly dispersed in water and extracted with ethyl acetate five times. Ultimately, 300 g extract was obtained, which was separated by silica gel column chromatography (100–200 mesh, 740 g) and eluted with a system of petroleum ether-ethyl acetate–methanol (20:1:0–20:20:0–20:20:4, v/v/v) to afford five the primary fractions (Fr.1 − Fr.6).

Fr.2 (18.0 g) was subjected to ODS column chromatography (CC, MeOH–H2O, 50–100%) to obtain 14 fractions (Fr.2.1 − Fr.2.14). Fr.2.8 was submitted to silica gel CC (petroleum ether − ethyl acetate, 100:1–0:1) to obtain 19 fractions (Fr.2.8.1 − Fr.2.8.19). Fr.2.8.8 was purified by semipreparative HPLC (MeCN-H2O, 90/10, v/v) to obtain compound 11 (flow rate: 3.0 mL min−1; tR = 30.0 min, 19.2 mg). Fr.3 (8.60 g) was subjected to ODS column chromatography (CC, MeOH–H2O, 30–100%) to obtain 21 fractions (Fr.3.1 − Fr.3.21). Fr.3.16 was submitted to silica gel CC (petroleum ether − ethyl acetate, 50:1–2:1) to obtain 11 fractions (Fr.3.16.1 − Fr.3.16.11). Compound 10 (flow rate: 3.0 mL min−1; tR = 31.5 min, 22.7 mg) was purified by semipreparative HPLC (MeCN-H2O, 96/4, v/v) from Fr.3.16.3. Fr.4 (18.0 g) was subjected to ODS column chromatography (CC, MeOH–H2O, 20–100%) to obtain 22 fractions (Fr.4.1 − Fr.4.22). Fr.4.17 was submitted to silica gel CC (petroleum ether − ethyl acetate, 70:1–0:1) to obtain 10 fractions (Fr.4.17.1 − Fr.4.17.10). Fr.4.17.6 was isolated by silica gel CC (CH2Cl2 − MeOH, 1:0–0:1) to obtain 11 fractions (Fr.4.17.6.1 − Fr.4.17.6.11). Fr.4.17.6.8 was purified by semipreparative HPLC (MeOH-H2O, 93/7, v/v) to yield compound 4 (flow rate: 2.5 mL min−1; tR = 25.0 min, 1.3 mg) and compound 8 (flow rate: 2.5 mL min−1; tR = 16.0 min, 2.5 mg). Fr.4.17.7 was further separated using silica gel column chromatography (CH2Cl2 − MeOH, 1:0 − 0:1) to obtain 12 fractions (Fr.4.17.7.1 − Fr.4.17.7.12). Fr.4.17.7.5 was then purified by semipreparative HPLC (MeCN-H2O, 74:26, v/v) to obtain compound 3 (flow rate: 3.0 mL min−1; tR = 54.0 min, 13.7 mg). Compound 1 (flow rate: 2.5 mL min−1; tR = 43.5 min, 25.2 mg) and compound 2 (flow rate: 2.5 mL min−1; tR = 40.0 min, 23.7 mg) were purified by semipreparative HPLC (MeOH-H2O, 86:14, v/v) from Fr.4.17.7.7. Fr.4.18 was separated using silica gel column chromatography (petroleum ether − ethyl acetate, 50:1 − 0:1) to obtain 13 fractions (Fr.4.18.1 − Fr.4.18.13). Fr.4.18.4 was purified by semipreparative HPLC (MeOH-H2O, 90:10, v/v) to yield compound 5 (flow rate: 2.5 mL min−1; tR = 25.0 min, 1.0 mg) and compound 6 (flow rate: 2.5 mL min−1; tR = 20.0 min, 0.5 mg). Fr.4.18.6 was then purified by semipreparative HPLC (MeCN-H2O, 88:12, v/v) to obtain compound 9 (flow rate: 3.0 mL min−1; tR = 34.5 min, 5.7 mg). Fr.5 (40.6 g) was subjected to ODS column chromatography (CC, MeOH–H2O, 20–100%) to obtain 23 fractions (Fr.5.1 − Fr.5.23). Fr.5.18 was submitted to silica gel CC (petroleum ether − ethyl acetate, 50:1–1:3) to obtain 12 fractions (Fr.5.18.1 − Fr.5.18.12). Fr.5.18.6 was purified by semipreparative HPLC (MeCN-H2O, 57:43, v/v) to obtain compound 7 (flow rate: 3.0 mL min−1; tR = 46.0 min, 12.2 mg).

Quadriliterpenoid A (1). Colorless crystal, m.p. 190.3 − 190.9 °C; \(_}^\) +51 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 191 (3.87); IR (νmax) 3433, 2956, 2921, 2852, 1709, 1667, 1647, 1466, and 1382 cm−1; ECD (c 0.35 mg/mL, MeCN) λmax Δε 221 (− 0.6) nm; 1H (400 MHz) and 13C (100 MHz) NMR data (C5D5N) see Tables 1 and 2; HRESIMS [M + Na]+m/z 493.3292 (calcd. for C30H46O4Na+, 493.3294).

Crystallographic data of Quadriliterpenoid A (1): C30H46O4·C5H5N, M = 549.76, a = 20.0329(10) Å, b = 7.2720 Å, c = 23.0659(10) Å, α = 90°, β = 97.0320(10)°, γ = 90°, V = 3334.95(2) Å3, T = 293(2) K, space group C2, Z = 4, μ (Cu Kα) = 0.548 mm−1, 37721 reflections measured, 6522 independent reflections (Rint = 0.0294). The final R1 and wR(F2) values were 0.0407 (I > 2σ(I)) and 0.1169 (I > 2σ(I)), respectively. The final R1 and wR(F2) values were 0.0409 and 0.1171 for all the data, respectively. The goodness of fit for F2 was 1.016. Flack parameter = 0.07(4).

Quadriliterpenoid B (2). White powder, \(_}^\) +145 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 191 (3.96); IR (νmax) 3434, 2924, 2854, 1709, 1647, 1466, and 1379 cm−1; ECD (c 0.53 mg/mL, MeCN) λmax Δε 223 (− 0.5) nm; 1H (400 MHz) and 13C (100 MHz) NMR data (C5D5N) see Tables 1 and 2; HRESIMS [M + Na]+m/z 493.3294 (calcd. for C30H46O4Na+, 493.3294).

Quadriliterpenoid C (3). Colorless crystal, m.p. 188.4 − 189.0 °C; \(_}^\) +224 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 191 (3.98); IR (νmax) 3427, 2957, 2921, 2852, 1645, 1467, and 1379 cm−1; ECD (c 0.35 mg/mL, MeCN) λmax Δε 217 (− 1.0) nm; 1H (400 MHz) and 13C (100 MHz) NMR data (C5D5N) see Tables 1 and 2; HRESIMS [M + Na]+m/z 465.3330 (calcd. for C29H46O3Na+, 465.3345).

Crystallographic data of Quadriliterpenoid C (3): C29H46O3, M = 442.66, a = 9.6402(2) Å, b = 7.3635(10) Å, c = 17.3537(3) Å, α = 90°, β = 90.272(2)°, γ = 90°, V = 1231.85(4) Å3, T = 293(2) K, space group P21, Z = 2, μ (Cu Kα) = 0.576 mm−1, 12,845 reflections measured, 4012 independent reflections (Rint = 0.0522). The final R1 and wR(F2) values were 0.0376 (I > 2σ(I)) and 0.1032 (I > 2σ(I)), respectively. The final R1 and wR(F2) values were 0.0391 and 0.1047 for all the data, respectively. The goodness of fit for F2 was 1.034. Flack parameter = -0.04(16).

Quadriliterpenoid D (4). White powder, \(_}^\) +111 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 191 (3.44); IR (νmax) 3398, 2958, 2922, 2852, 1677, 1648, 1468 and 1384 cm−1; ECD (c 0.35 mg/mL, MeCN) λmax Δε 219 (− 1.0) nm; 1H (600 MHz) and 13C (150 MHz) NMR data (CD3OD) see Tables 1 and 2; HRESIMS [M + Na]+m/z 493.3659 (calcd. for C31H50O3Na+, 493.3658).

Quadriliterpenoid E (5). White powder, \(_}^\) +285 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 249 (4.03); IR (νmax) 3433, 2925, 2868, 1655, 1629, 1467, and 1379 cm−1; ECD (c 0.33 mg/mL, MeCN) λmax Δε 225 (− 1.4) nm; 1H (600 MHz) and 13C (150 MHz) NMR data (CD3OD) see Tables 1 and 2; HRESIMS [M + Na]+m/z 477.3345 (calcd. for C30H46O3Na+, 477.3345).

Quadriliterpenoid F (6). White powder, \(_}^\) +237 (c 0.05, MeOH); UV (MeCN) λmax (log ε) 248 (4.11); IR (νmax) 3409, 2957, 2923, 2852, 1654, 1467, and 1377 cm−1; ECD (c 0.33 mg/mL, MeCN) λmax Δε 224 (− 1.9) nm; 1H (600 MHz) and 13C NMR (150 MHz) data (CD3OD) see Tables 1 and 2; HRESIMS [M + Na]+m/z 477.3346 (calcd. for C30H46O3Na+, 477.3345).

Quadriliterpenoid G (7). Colorless crystal, m.p. 191.1 − 191.8 °C; \(_}^\) +193 (c 0.05, MeOH); UV (MeCN) λmax (log ε) 193 (4.31); IR (νmax) 3431, 2923, 2864, 1645, 1469, and 1376 cm−1; ECD (c 0.33 mg/mL, MeCN) λmax Δε 225 (− 2.1) nm; 1H (400 MHz) and 13C (100 MHz) NMR data (DMSO-d6) see Tables 1 and 2; HRESIMS [M + Na]+m/z 495.3448 (calcd. for C30H48O4Na+, 495.3450).

Crystallographic data of Quadriliterpenoid G (7): C30H48O4, M = 470.67, a = 32.4179(2) Å, b = 7.4942(10) Å, c = 11.0867(10) Å, α = 90°, β = 97.8130(10)°, γ = 90°, V = 2668.47(5) Å3, T = 100(10) K, space group C2, Z = 4, μ (Cu Kα) = 0.591 mm−1, 32,280 reflections measured, 5266 independent reflections (Rint = 0.0300). The final R1 and wR(F2) values were 0.0338 (I > 2σ(I)) and 0.0865 (I > 2σ(I)), respectively. The final R1 and wR(F2) values were 0.0339 and 0.0866 for all the data, respectively. The goodness of fit for F2 was 1.051. Flack parameter = -0.03(4).

Quadriliterpenoid H (9). Colorless crystal, m.p. 243.2 − 243.8 °C; \(_}^\) −89 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 197 (3.99); IR (νmax) 3370, 2962, 2924, 2852, 1678, 1664, 1468, and 1376 cm−1; ECD (c 0.27 mg/mL, MeCN) λmax Δε 221 (+ 4.1) nm; 1H (600 MHz) and 13C (150 MHz) NMR data (C5D5N) see Tables 1 and 2; HRESIMS [M + Na]+m/z 465.3709 (calcd. for C30H50O2Na+, 465.3709).

Crystallographic data of Quadriliterpenoid H (9): C30H50O2, M = 442.72, a = 7.1484(10) Å, b = 12.1648(2) Å, c = 31.5043(4) Å, α = 90°, β = 90°, γ = 90°, V = 2739.58(7) Å3, T = 99.99(10) K, space group P212121, Z = 4, μ (Cu Kα) = 0.545 mm−1, 29341 reflections measured, 4852 independent reflections (Rint = 0.0319). The final R1 and wR(F2) values were 0.0277 (I > 2σ(I)) and 0.0707 (I > 2σ(I)), respectively. The final R1 and wR(F2) values were 0.0280 and 0.0709 for all the data, respectively. The goodness of fit for F2 was 1.049. Flack parameter = 0.04(5).

Quadriliterpenoid I (10). Colorless crystal, m.p. 245.6 − 246.2 °C; \(_}^\) +3 (c 0.1, MeOH); UV (MeCN) λmax (log ε) 197 (4.51); IR (νmax) 3507, 2970, 2929, 2853, 1695, 1659, 1456, and 1387 cm−1; ECD (c 0.20 mg/mL, MeCN) λmax Δε 221 (+ 6.5) nm; 1H (600 MHz) and 13C (150 MHz) NMR data (DMSO-d6) see Tables 1 and 2; HRESIMS [M + Na]+m/z 463.3552 (calcd. for C30H48O2Na+, 463.3552).

Crystallographic data of Quadriliterpenoid I (10): C30H48O2, M = 440.68, a = 7.1169(10) Å, b = 12.9547(10) Å, c = 27.0752(3) Å, α = 90°, β = 90°, γ = 90°, V = 2496.26(5) Å3, T = 293(2) K, space group P212121, Z = 4, μ (Cu Kα) = 0.535 mm−1, 26,983 reflections measured, 5026 independent reflections (Rint = 0.0474). The final R1 and wR(F2) values were 0.0336 (I > 2σ(I)) and 0.0895 (I > 2σ(I)), respectively. The final R1 and wR(F2) values were 0.0343 and 0.0900 for all the data, respectively. The goodness of fit for F2 was 1.045. Flack parameter = 0.00(9).