Phenanthrenoid

Phenanthrenoids are chemical compounds formed with a phenanthrene backbone. These compounds occur naturally in plants, although they can also be synthesized.^[1]

Chemical structure of gymnopusin, a chemical compound found in orchids

Phenanthrols

Phenanthrols are any of five isomeric phenols derived from phenanthrene (1-phenanthrol, 2-phenanthrol, 3-phenanthrol, 4-phenanthrol, 9-phenanthrol). These molecules can be biomarkers of smoking and/or PAH worker exposure.^[2]

Chemistry

Under UV irradiation, stilbene and its derivatives undergo intramolecular cyclization to form dihydrophenanthrenes.

Natural occurrences

Phenanthrenes have been reported from flowering plants, mainly in the family Orchidaceae, and a few in the families Dioscoreaceae, Combretaceae and Betulaceae, as well as in the lower plant class Marchantiophyta (liverworts).^[3]

The rhizome of Dioscorea communis contains phenanthrenes (7-hydroxy-2,3,4,8-tetramethoxyphenanthrene, 2,3,4-trimethoxy-7,8-methylenedioxyphenanthrene, 3-hydroxy-2,4,-dimethoxy-7,8-methylenedioxyphenanthrene, 2-hydroxy-3,5,7-trimethoxyphenanthrene and 2-hydroxy-3,5,7-trimethoxy-9,10-dihydrophenanthrene).^[4]

The dimeric phenanthrenoid 8,8'-bidehydrojuncusol and the monomeric dehydrojuncusol can be isolated from Juncus acutus.^[5]

Perakensol is a phenanthrenoid that can be isolated from Alseodaphne perakensis.^[6]

In orchids

Phenanthrenes have been reported in species of Dendrobium, Bulbophyllum, Eria, Maxillaria, Bletilla, Coelogyne, Cymbidium, Ephemerantha and Epidendrum.^[3]

3,4,8-Trimethoxyphenanthrene-2,5-diol is one of the 17 phenanthrenes found in the extract of the stems of the orchid Dendrobium nobile.^[7][8]

Three phenanthrenes can be isolated from the stems of the orchid Flickingeria fimbriata. The structures are 2,5-dihydroxy-4,9,10-trimethoxyphenanthrene, 2,5-dihydroxy-4-methoxyphenanthrene and 2,5,9-trihydroxy-4-methoxy-9,10-dihydrophenanthrene. These molecules are named plicatol A, B and C.^[9]

Nudol is a phenanthrene from the orchids Eulophia nuda, Eria carinata and Eria stricta.^[10] 9,10-Dihydro-2,5-dimethoxyphenanthrene-1,7-diol is a phenanthrene from Eulophia nuda. This compound shows cytotoxic activity against human cancer cells.^[11]

2,7-Dihydroxy-3,6-dimethoxyphenanthrene is a phenanthrene from Dehaasia longipedicellata.^[12]

Bulbophyllum gymnopus produces the phenanthrenediol gymnopusin.^[13]

Bulbophyllum reptans contains gymnopusin, confusarin (2,7-dihydroxy-3,4,8-trimethoxyphenanthrene), 2,7-dihydroxy-3,4,6-trimethoxyphenanthrene and its 9,10-dihydro derivative, flavanthrinin (2,7-dihydroxy-4-methoxyphenanthrene) and its 9,10-dihydro derivative (coelonin), cirrhopetalanthrin (2,2′,7,7′-tetrahydroxy-4,4′-dimethoxy-1,1′-biphenanthryl), its 9,9′,10,10′-tetrahydro derivative (flavanthrin) and the dimeric phenanthrenes reptanthrin and isoreptanthrin.^[14]

Bulbophyllum vaginatum contains the two phenanthrenes 4,9-dimethoxyphenanthrene-2,5-diol and 4,6-dimethoxyphenanthrene-2,3,7-triol, and the two dihydrophenanthrenes 4-methoxy-9,10-dihydrophenanthrene-2,3,7-triol and 4,6-dimethoxy-9,10-dihydrophenanthrene-2,3,7-triol.^[15]

Coelogyne cristata contains coeloginanthridin (3,5,7-trihydroxy-1,2-dimethoxy-9,10-dihydrophenanthrene), a 9,10-dihydrophenanthrene derivative, and coeloginanthrin (3,5,7-trihydroxy-1,2-dimethoxyphenanthrene), the corresponding phenanthrene analogue, coelogin and coeloginin.^[16]

Orchinol and loroglossol have a phytoalexin effect and reduce the growth of Cattleya aurantiaca seedlings.^[17]

The phenanthrenes 2,5-dihydroxy-3,4-dimethoxyphenanthrene, 9,10-dihydro-2,5-dihydroxy-3,4-dimethoxyphenanthrene, 2,7-dihydroxy-3,4-dimethoxyphenanthrene (nudol), 9,10-dihydro-2,7-dihydroxy-3,4-dimethoxyphenanthrene, 2,5-dihydroxy-3,4,9-trimethoxyphenanthrene and 2,7-dihydroxy-3,4,9-trimethoxyphenanthrene can be isolated from Maxillaria densa.^[18]

Cirrhopetalanthrin is a dimeric phenanthrene derivative from Cirrhopetalum maculosum.^[19]

Glycosides

Five phenanthrene glycosides, denneanoside A, B, C, D and E and one 9,10-dihydrophenanthrene glycoside, denneanoside F, can be isolated from the stem of Dendrobium denneanum.^[20]

Metabolism

Cis-3,4-dihydrophenanthrene-3,4-diol dehydrogenase is an enzyme that uses (+)-cis-3,4-dihydrophenanthrene-3,4-diol and NAD+ to produce phenanthrene-3,4-diol, NADH and H+. This enzyme participates in naphthalene and anthracene degradation.

See also

• (+)-Cavicularin, a cyclic bibenzyl-dihydrophenanthrene derivative^[21]