Friday, April 9, 2010

Liverworts and Their Phytochemistry

Liverworts are classified as bryophytes, and are distinguished from the other members of this order (mosses and hornworts) by having either flat-lobed leaf-stem structures or small leaves in rows of three. They can be found on tree trunks or growing on exposed soil, often in association with mosses. As such, they can become a troublesome weed in some horticultural situations (e.g., Lunularia cruciata).

Lunularia cruciata

Liverworts are ungrazed by animals, fungi and bacteria. This suggests that they contain antifeedant phytochemicals as morphologically they appear quite lush and succulent. Further evidence for their phytochemical activity can be seen in the history of the use of liverworts (along with other byrophytes) to cure cuts, burns and external wounds and as treatment for bacteriosis, pulmonary tuberculosis, neurasthenia, fractures, convulsions, scalds, uropathy, pneumonia and neurasthenia. While some of this may be attributed to the doctrine of signatures, they erroneous idea that plants shaped like body parts copuld be used to treat said body part research has shown that 700 terpenoids and 220 aromatic compounds have been isolated from liverworts, many of which show interesting biological activity. Liverworts are a greater source than the other Bryophytes of biochemicals as they contain cellular oil bodies, which are composed of lipophilic terpenoids and aromatic compounds (Asakawa(2001), Phytochemistry 56 pp. 297-312).

An example of one such phytochemical is Marchantin A. This bis(bibenzyl) is commonly found in Marchantiales species such as Marchantia polymorpha and shows antifungal, antimicrobial and muscle relaxing and cytotoxic activities.

Marchantia polymorpha

Due to the lack of a fossil record for bryophytes, the evolution of liverworts is unclear. However, two theories exit. The first is the progressive theory that suggests that bryophytes arose from algae and in turn gave rise to the pterioophytes (ferns and their allies such as horsetails and quillworts). The second (the reductive theory) suggests that green algae dave rise to primitive ancestor of vascular plants from which both the bryophytes and pteridophytes arose. Currently, researches at the Tokushima Bunri University in Tokushima, Japan are attempting to solve this riddle by examining the phytochemical links between the two orders.

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