Briarenols I—K, New Anti-inflammatory 8,17-Epoxybriaranes from the Octocoral Briareum excavatum (Briareidae)

Abstract

Five 8,17-epoxybriaranes, including three new compounds-briarenols I-K (1-3), along with two known analogues, briaexcavatolide P (4) and briaexcavatin P (5), were isolated from the octocoral Briareum excavatum. The structures of briaranes 1-3 were elucidated by spectroscopic methods, including 1D and 2D NMR studies and (+)-HRESIMS. Briarane 4 exerted inhibition effects on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) release from RAW 264.7.Molecules 2020, 25, 1405 2 of 9 ( Figure 1). In the current study, the comprehensive workflow of isolation, structure determination, and anti-inflammatory activity evaluation, was implemented on briaranes 1-5.Molecules 2020, 25, x FOR PEER REVIEW 2 of 9 briaexcavatin P (5) [9], (Figure 1). In the current study, the comprehensive workflow of isolation, structure determination, and anti-inflammatory activity evaluation, was implemented on briaranes 1-5. 1: R1 = OAc, R2 = R6 = OH, R3 = n-OC(O)Pr, R4 = H, R5 = β-OH 2: R1 = R2 = OH, R3 = OAc, R4 = R6 = H, R5 = β-OH 3: R1 = OAc, R2 = R3 = R6 = H, R4 = OH, R5 = β-OH 4: R1 = OAc, R2 = OH, R3 = n-OC(O)Pr, R4 = R6 = H, R5 = β-OH 5: R1 = R3 = OAc, R2 = OH, R4 = R6 = H, R5 = β-OH 6: R1 = OAc, R2 = n-OC(O)Pr, R3 = R4 = R6 = H, R5 = β-OH 7: R1 = OAc, R2 = R3 = R6 = H, R4 = OH, R5 = α-OH Figure 1. Structures of briarenols I-K (1-3), briaexcavatolide P (4), briaexcavatin P (5), excavatolide B (6), and briareolide B (7).

Briarenols W–Z: Chlorine-Containing Polyoxygenated Briaranes from Octocoral Briareum stechei (Kükenthal, 1908)

“…Since briarein A, a 3,8-cyclized cembranoid (briarane), was first reported from a Caribbean octocoral Briareum asbestinum (Pallas, 1766) in 1977 [1], hundreds of marine origin briarane diterpenoids with novel structures and extensive bioactivities have been obtained from various octocorals [2,3], of which octocorals belonging to the genus Briareum have been recognized as the most important source of briarane-type natural products [3]. In our previous studies, a series of interesting briarane-type diterpenoids, including briarenols A-T [4][5][6][7][8][9][10][11][12], were isolated from various octocorals belonging to the genera Briareum, Junceella, and Ellisella, collected off the waters of Taiwan, and an anti-inflammatory assay was employed to evaluate the activities of these compounds in reducing the release of inducible natural products [3]. In our previous studies, a series of interesting briarane-type diterpenoids, including briarenols A-T [4][5][6][7][8][9][10][11][12], were isolated from various octocorals belonging to the genera Briareum, Junceella, and Ellisella, collected off the waters of Taiwan, and an anti-inflammatory assay was employed to evaluate the activities of these compounds in reducing the release of inducible oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) in an in vitro pro-inflammatory macrophage culture model.…”

“…Therefore, cultured octocoral Briareum stechei (Kükenthal, 1908) [14], originally dwelling in the waters of Taiwan, was selected for chemical investigation in our study. The results identified eight chlorine-containing briaranes, including four new compounds, briarenols W-Z (1-4), together with known briaranes, solenolide A (5) [15], briarenolide M (6) [16], briaexcavatolide F (7) [17], and brianolide (8) [18] (Figure 1). This study carried out the isolation and identification of the isolates as well as analyzing their bioactivity.…”

“…This study carried out the isolation and identification of the isolates as well as analyzing their bioactivity. 6), briaexcavatolide F (7), brianolide (8), and a picture of cultured B. stechei.…”

Polyoxygenated Klysimplexane- and Eunicellin-Based Diterpenoids from the Gorgonian Briareum violaceum

“…Gorgonian corals belonging to genus Briareum (Cnidaria, Octocorallia, Briareidae) inhabiting the western Pacific Ocean and Caribbean waters have been found to be a rich source of diterpenoids [ 1 , 2 ] possessing fused bicarbocyclic structures of briarane [ 3 , 4 , 5 , 6 , 7 ], eunicellin [ 8 , 9 , 10 , 11 ], and asbestinane [ 12 , 13 , 14 ] types, in addition to cembranoids [ 15 , 16 ]. Many of these metabolites exhibit a wide range of bioactivities, including anti-inflammatory [ 3 , 11 , 17 , 18 , 19 , 20 ], cytotoxic [ 14 , 21 , 22 , 23 ], antiviral [ 14 , 21 , 24 ], antimalarial [ 8 ], antimicrobial [ 14 ], and analgesic [ 20 ] activities.…”

Food and Drug Analysis

“…Their structures were elucidated by spectroscopic methods, including 1D and 2D nuclear magnetic resonance (NMR) studies and high resolution electrospray ionization mass spectrometry (HRESIMS) analysis. One briarane-type isolate exerted inhibition effects on inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) release from RAW 264.7 [6].…”