*3.3. Extraction and Isolation*

The freeze-dried and sliced bodies (wet/dry weight = 1344/568 g) of the specimen were extracted with supercritical CO2 to give 58.9 g of extract. Partial extract (36.4 g) was then applied on silica gel column and eluted with gradients of *n*-hexane/EtOAc to furnish fractions A−K. Fraction F was purified by NP-HPLC using a mixture of *n*-hexane/acetone (4:1) to yield fractions F1−F13. Fraction F6 was repurified by RP-HPLC, using a mixture of MeOH/H2O (60:40; at a flow rate = 4 mL/min) to afford **4** (6.7 mg). Fraction G was separated by NP-HPLC, using a mixture of *n*-hexane/acetone (3:1) to yield fractions G1−G12. Fractions G6 and G7 were repurified by RP-HPLC using a mixture of MeOH/H2O (60:40; at a flow rate = 4.0 mL/min) to afford **5** (1.3 mg) and **3** (1.0 mg), respectively. Fraction H was separated by NP-HPLC using a mixture of *n*-hexane and acetone (3:1) to yield fractions H1−H18. Fractions H12 and H15 were repurified by RP-HPLC, using a mixture of MeOH/ H2O (60:40; at a flow rate = 4.0 mL/min) to afford **2** (2.1 mg) and **1** (0.6 mg), respectively.

Briarenol I (**1**): Amorphous powder; [α] 22 <sup>D</sup> + 207 (*c* 0.03, CHCl3), IR (ATR) νmax 3524, 1783, 1736, 1222, 891 cm−1; 13C (100 MHz, CDCl3) and 1H (400 MHz, CDCl3) NMR data (see Tables 1 and 2); ESIMS: *m*/*z* 649 [M + Na]+; HRESIMS *m*/*z* 649.24677 (calculated for C30H42O14 + Na, 649.24668).

Briarenol J (**2**): Amorphous powder; [α] 26 <sup>D</sup> + 140 (*c* 0.08, CHCl3), IR (ATR) νmax 3483, 1779, 1727, 1220, 890 cm−1; 13C (100 MHz, CDCl3) and 1H (400 MHz, CDCl3) NMR data (see Tables 1 and 2); ESIMS: *m*/*z* 563 [M + Na]+; HRESIMS *m*/*z* 563.21007 (calculated for C26H36O12 + Na, 563.20990).

Briarenol K (**3**): Amorphous powder; [α] 23 <sup>D</sup> + 37 (*c* 0.06, CHCl3), IR (ATR) νmax 3468, 1780, 1739, 1255, 892 cm−1; 13C (100 MHz, CDCl3) and 1H (400 MHz, CDCl3) NMR data (see Tables 1 and 2); ESIMS: *m*/*z* 547 [M + Na]+; HRESIMS *m*/*z* 547.21514 (calculated for C26H36O11 + Na, 547.21498).

Briaexcavatolide P (**4**): Amorphous powder; [α] 24 <sup>D</sup> + 182 (*c* 0.3, CHCl3) (ref. [8], [α]27D + 167 (*c* 1.0, CHCl3)), IR (ATR) νmax 3513, 1783, 1731, 1218, 889 cm−1; 1H and 13C NMR data were found to be in agreement with previous study [8]; ESIMS: *m*/*z* 633 [M + Na]+.

Briaexcavatin P (**5**): Amorphous powder; [α] 23 <sup>D</sup> + 134 (*c* 0.05, CHCl3) (ref. [9], [α] 25 <sup>D</sup> + 198 (*c* 0.08, CHCl3)), IR (ATR) νmax 3503, 1785, 1735, 1240, 889 cm−1; 1H and 13C NMR data were found to be in agreement with previous study [9]; ESIMS: *m*/*z* 605 [M + Na]+.

#### *3.4. In Vitro Anti-inflammatory Assay*

The proinflammatory suppression assay was employed to assess the activities of the isolated compounds **1**–**5** against the release of iNOS and COX-2 from macrophage cells as the literature reported [13–15].

#### **4. Conclusions**

*B. excavatum* was demonstrated to have a wide structural diversity of briarane-type diterpenoids that possessed various pharmacological properties, especially in anti-inflammatory activity. In our continued study on *B. excavatum*, three previously unreported briaranes, briarenols I–K (**1**–**3**), along with the known analogues, briaexcavatolide P (**4**) and briaexcavatin P (**5**), were isolated. In the present study, the anti-inflammatory activity of **1**–**5** was assessed using inhibition of pro-inflammatory iNOS and COX-2 release from macrophages. The results indicated that briaexcavatolide P (**4**) showed the most potent suppressive effect on iNOS release.

**Supplementary Materials:** The Supplementary Materials are available online. ESIMS, HRESIMS, IR, 1D and 2D NMR spectra of new compounds **1**–**3**.

**Author Contributions:** Conceptualization, L.-S.F., Y.-J.W., Z.-H.W. and P.-J.S; investigation, T.-H.H., Y.-H.C., B.-R.P., Y.-Y.C., L.-G.Z. and J.-J.C.; writing—original draft preparation, T.-H.H. and P.-J.S.; writing—review and editing, T.-C.L. and P.-J.S. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by grants from the National Museum of Marine Biology and Aquarium; the National Dong Hwa University; and the Ministry of Science and Technology, Taiwan (Grant Nos: MOST 106-2320-B-291-001-MY3 and 107-2320-B-291-001-MY3) awarded to Ping-Jyun Sung.

**Conflicts of Interest:** The authors declare no conflicts of interest.
