New Cytotoxic Briaran Diterpenes from the Formosan Gorgonian Briareum sp.

Abstract

Three new briaran diterpenes, 2β-acetoxy-2-(debutyryloxy)stecholide E (3), 9-deacetylstylatulide lactone (4), and 4β-acetoxy-9-deacetylstylatulide lactone (5), and two known diterpenes, brianthein W (1) and 9-deacetylbriareolide H (2), have been isolated from a Briareum sp. of gorgonian. The structures and relative stereochemistry of these compounds were determined by spectroscopic and chemical methods. Diterpenes 2−4 and the corresponding 9-acetyl derivatives 6, 7, and 12 exhibited cytotoxicity toward various cancer cell lines.

New Briarane Diterpenoids from Taiwanese Soft Coral Briareum violacea

“…In addition, six known briaranes, solenolides A and D [25], excavatolide A [26], briaexcavatolide I [22], 4β-acetoxy-9-deacetystylatulide lactone and 9-deacetylstylatulide lactone [27], were identified. The new isolated briaranes 1 – 10 and derivative 11 were evaluated for anti-inflammatory activities on superoxide-anion generation and elastase release by human neutrophils in response to N -formyl-methionyl-leucyl-phenylalanine (fMLP)/Cytochalasin B (CB).…”

Briarane Diterpenoids Isolated from Octocorals between 2014 and 2016

“…Sixteen briarane diterpenoids, including 10 new 8-hydroxybriaranes, briaviolides A–J ( 1 – 10 ) (Figure 2), and six known metabolites, solenolides A [10] and D (=briaexcavatolide E) [1,10,11,12], excavatolide A [13], briaexcavatolide I [12], 4β-acetoxy-9-deacetylstylatulide lactone, and 9-deacetylstylatulide lactone [14], were isolated from the octocoral Briareum violacea , collected from the waters of Taiwan [15]. The structures of new briaranes 1 – 10 were established by chemical and spectroscopic methods, and determination of the absolute configuration of briaviolide A ( 1 ) was completed by X-ray diffraction analysis of its monobenzoyl derivative [15].…”

Secondary Metabolites from the South China Sea Invertebrates: Chemistry and Biological Activity

“…Junceelolide C (603) was isolated again from J. juncea [270] which also produced an additional eight analogues, namely juncenolides A-D (619-622) [270,271] and juncins N-Q (623-626) [272,273]. Five briarane analogues, brianthein W (627), 9-deacetylbriareolide H (628), 2β-acetoxy-2-(debutyryloxy) stecholide E (629), 9-deacetylstylatulide lactone (630), and 4β-acetoxy-9-deacetylstylatulide lactone (631) [274], were isolated from an unidentified species of the genus Briareum which is known for generating the first briarane diterpenoid, briarein A [275]. Extensive chemical investigation on B. excavatum resulted in the isolation of a large group of briaranes, namely the excavatolides A-M (632-644) [276,277] and U-Z (645-650) [278], the briaexcavatolides A-Z (651-676) [279][280][281][282][283][284], as well as the brianolides 677 and 678 [276,280].…”

“…The natural briarane diterpenoids are commonly cytotoxic compounds. Many briareins, such as brianthein W (627), 9-deacetylbriareolide H (628), 2β-acetoxy-2-(debutyryloxy) stecholide E (629), 9-deacetylstylatulide lactone (630) [274], the excavatolides A (632), D (635) [276], U (645), and Z (650) [278], the briaexcavatolides B (652), F (656) [279], and L (662) and brianolide 678 [280], displayed potent selective cytotoxic activities against one or several of the P-388, KB, A549, and HT-29 cell lines. The excavatolides C (634), E (636), K (642), and M (644) were broadly cytotoxic against a limited panel of these cells [276,277] with an extraordinarily low ED 50 value of 0.001 µg/mL being observed for excavatolide M (644) against P-388 [277].…”

“…For example, variations in the functional groups at the C-2, C-3, C-9, and C-12 positions can influence the cytotoxicity of these compounds [277]. The presence of a large substituent at C-3 significantly reduces the cytotoxicity of this class of compounds [278] while oxidation at C-9 increases the level of activity of these diterpenoids [274].…”