Plant photosensitizers: A survey of their occurrence in arid and semiarid plants from North America

Abstract

Various plants native to arid and semiarid habitats throughout the southwestern United States, Baja California, and northern Mexico were bioassayed for phototoxic natural products. Approximately 115 species representing 57 genera and eight plant families were assayed for phototoxic activity by standard antimicrobial techniques usingEscherichia coli andSaccharomyces cerevisiae. Phototoxic constituents were extracted from numerous members in the Asteraceae (Compositae) and occurred with highest frequency among species of the subtribe Pectidinae (tribe Heliantheae). Extracts ofPectis, the largest genus in the Pectidinae, had substantial light-activated biocidal action despite the paucity of acetylenic thiophenes, the phototoxins characteristic of most other genera in the subtribe. Leaf resin from the creosote bush [Larrea tridentata (Sesse & Mol. ex DC.) Coville; Zygophyllaceae], a dominant desert shrub, possessed potent antimicrobial activity in the absence of light; however, the toxicity of this extract was slightly enhanced in the presence of UVA irradiation. Phototoxic antimicrobials were not detected in extracts of selected species from the Asclepiadaceae, Chenopodiaceae, Hydrophyllaceae, Lamiaceae, Polygonaceae, or Solanaceae.

Phylogenetic Relationships Between and within Phacelia Sections Whitlavia and Gymnobythus (Boraginaceae)

“…Pectis angustifolia has a high thimole content (Albers, 1942), and Pectis papposa has been suggested as a potential source of commercial food and beverage flavoring because of its high cumaldehyde and carvone content (Bradley & HaagenSmit, 1949). Phototoxic, antibacterial, and antifungal properties of Pectis oil have been reported (Downum et al, 1985;Downum & Rodriquez, 1986;Downum et al, 1989;da Silva et al, 2005;Soares et al, 2009). Pectis is noteworthy because some species previously surveyed were shown to use C 4 photosynthesis, a photosynthetic pathway that confers enhanced efficiency in conditions of high heat and high light intensity (Sage et al, 2011).…”

Molecular Phylogeny ofPectis(Tageteae, Asteraceae), a C4Genus of the Neotropics, and its Sister GenusPorophyllum

“…Pectis angustifolia has a high thimole content (Albers, 1942), and Pectis papposa has been suggested as a potential source of commercial food and beverage flavoring because of its high cumaldehyde and carvone content (Bradley & Haagen-Smit, 1949). Phototoxic, antibacterial, and antifungal properties of Pectis oil have been reported (Downum et al, 1985;Downum & Rodriquez, 1986;Downum et al, 1989;da Silva et al, 2005;Soares et al, 2009). Pectis is noteworthy because some species previously surveyed were shown to use C 4 photosynthesis, a photosynthetic pathway that confers enhanced efficiency in conditions of high heat and high light intensity (Sage et al, 2011).…”

Zygophyllaceae R.Br.

“…With respect to livestock, in vitro studies also indicate that NDGA is a photoactive compound capable of causing photosensitization (Downum and Rodriguez 1986;Downum et al 1989). The structural similarity of the Larrea lignan NDGA, and its metabolites, to diethylstilbesterol suggests the possibility of hepatotoxic effects similar to those caused by estrogens (Obermeyer et al 1995).…”