## 2 Classes of Secondary Metabolites
### Diterpenes
Three diterpenes, sarcophytol **35**, sarcophytolide B **36**, and sarcophytolide C **37**, were reported from _S. glaucum_[34]. Sarcophytonolides A-D **38-41**, four cembranolides were isolated from _S. tortuousum_. Sarcophytonolide B **39** was found to be the 12-(methoxycarbonyl) derivative of compound **38**, in which it exhibited \(\alpha\beta\)-unsaturated methyl ester instead of the methyl group. Sarcophytonolide D **41** was similar in structure to compound **40**, while, compound **41** possessed an extra trisubstituted C=Cand acetoxy group [36]. Four more sarcophytonolides E-H **42-45** from _S. latum_ were isolated. All isolated compounds were related in structure to compound **40**, with an \(\alpha\), \(\beta\)-unsaturated butanolide group. Sarcophytonolide G **44** was found to be the epimer of Sarcophytonolide F **43** at C-6, while sarcophytonolide H **45** was 14-acetoxy methoxycarbonyl derivative of compound **43**. The absolute configuration was investigated by using the modified Mosher's assay as they all possessed secondary alcohol at C-6. It is worth noting that the structural configuration supporting all membrane diterpenes stated, in the order alcyanacea, with the identified absolute configuration at C-1, belonged to \(\alpha\)-series [37]. Moreover, sarcophytonolides I-L **46-49** were isolated from _S. latum_. All compounds were related in structure to the previously isolated compounds **38-45**; all possessed \(\alpha\), \(\beta\)-unsaturated butenolactone group. The absolute configuration of compounds **38-45** still need further determination. Considering the fact that these compounds were structurally related to previously isolated sarcophytonolide, the structure of sarcophytonolide I **46** differs from sarcophytonolide D **41**, in the olefinic C\({}_{7}\)=C\({}_{8}\) bond and absence of C=O group at C6 [38]. Another five cembranolide, sarcophytonolides N-R **50-54**, ketoblide **55**, and (_E,E,E_)-1-isopropyl-4,8,12-trimethylcylctetradeca-3,7,11-tiene **56** were isolated from _S. trocheliophorum_ Marenzeller. A detailed spectroscopic analysis was done, in which sarcophytonolides N-R **50-54** were found to be either mono- or bicyclic cembranoids possessing oxidized methyl groups and three/four double bonds [39]. The absolute configuration of another six metabolites isolated from _S. trocheliophorum_, sarcophytonolides S-U **57-59** and sartrolides H-J; \(\alpha\),\(\beta\)-unsaturated \(\varepsilon\)-lactone **60-62**, along with seven known analogues, were carried out through different techniques [40]. Chemical determination of _S. trocheliophorum_ yielded seven cembranolides, sartrolides A-G **63-69** and bissartrolide dimer **70**; a third member of this scarce class of cembran dimers [41]. Yalongenes A and B **71** and **72** another two cembranoids, isolated from _S. trocheliophorum_[42], and another two cembranoids, trochelioids A and B **73** and **74**, and 16-oxosarcophytonin E **75** were isolated [43]. Five diterpenes cembranc type, sarcrassins A-E **76-80**, beside emblide **81** isolated from _S. crassocoule_ were identified based on 1D and 2D NMR. Sarcrassins B and C **77** and **78**, cyclic diterpenes, derivatives of sarcrassin A **76** in which the double bond in sarcrassin A **76** was replaced by an epoxy ring in sarcrassin B **77**. However, in sarcrassin C **78** the epoxy ring in sarcrassin A **76** was replaced by a hydroxyl and methoxy group. As for sarcrassin D **79**, its bicyclic diterpene structure was confirmed through spectral data [44], and its absolute configuration, as well as that of emblide **81**, was determined by X-ray analysis [41; 45]. Investigation of ethyl acetate extract of _S. crassocoule_ yielded six polyoxygenated membrane-diterpens with a trans-fused \(\alpha\)-methylene-\(\gamma\)-lactone, identified as crassocolides A-F **82-87** alongside lobophytolide **88**. Absolute configuration for crassocolide A **82** was resolved by using modified Mosher's method [46].