Phototoxin-containing plant

Table II. Distribution of Phototoxin-Containing Plant Families...

The broad-spectrum biocidal action induced by phototoxic allelochemicals has been demonstrated toward a range of organisms including bacteria, fungi, nematodes, insects as well as non-photo-toxin-containing plants. Table III summarizes the organisms susceptible to photosensltlzatlon by alpha-terthienyl, a phototoxin characteristic of many Asteraceae species (4, 10-11). The toxicity of this thiophenic polyine toward plant pathogens (e.g.,... 

Plant metabolites that are capable of becoming toxic in sunlight or UVA are produced by a wide variety of biochemical pathways and thus are a structurally diverse group of natural products. Both linear and cyclic photosensitizers are known from plants. Linear phototoxins are generally derived from fatty acid precursors and typically possess conjugated double and triple bond systems. The majority of cyclic photosensitizers, on the other hand, are bi- and tricyclic aromatic molecules that may contain nitrogen, oxygen or sulfur as heterocyclic elements. 

Chemicals that are potentially capable of phototoxic action have been Isolated from more than 30 flowering plant families. Their occurrence among Important monocot and dlcot families is shown in Table 1. Most of the taxa represented in this table synthesize several types of photosensitizers. Members of the Asteraceae (sunflower family) and the Rutaceae (citrus family) for example synthesize the widest range of phototoxic compounds. Other families (e.g., Hypericaceae, Llliaceae, Moraceae and Orchidaceae) either lack or fail to express such biosynthetic diversity. Plants from these latter groups contain phototoxins derived from a single metabolic pathway. 

Various biosynthetic classes of phototoxic compounds have been isolated from over thirty plant families (5). Some plant families produce more than one type of phototoxin. Three different types of phototoxins have been isolated from the Apiaceae ( celery family), for example, and eight different types have been identified so far from the Rutaceae (citrus family). Among other families that contain phototoxins are the Asteraceae (sunflower family), Euphorbiaceae (spurge family), Fabaceae (pea family) and Moraceae (fig family) ( i). 

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