The Geography of Phytochemical Races

5.2 Nonvascular Plants 233
(see Fig. 5.7 for structures 459–465). Variations on the hybertane-type involved
the number of hydroxyl groups on the aromatic ring, which ranged from none to
three. The second set of compounds, the mastigophorones, varied in the nature of
the interaromatic ring linkage (Asakawa et al., 1991). Subsequently, Leong and
Harrison (1997) investigated a sample of the liverwort from West Malaysia. Neither
of the compound types described from eastern plants was observed. Three other
compounds were observed, however, and shown to be the known ent- trachyloban-
18-oic acid [462] and ent-trachyloban-19-oic acid [463], and the new ent-18hydroxytrachyloban-19-oic
acid [464]. As in many, if not most, of the situations
described in this review, no explanation for the chemical differences between the
two populations is evident (or was offered). Trachylobane derivatives are rare natural
products, but one, ent-3β,18-dihydroxytrachyloban-19-oic acid [465], has been
reported from the liverwort Jungermannia exsertifolia Steph. subsp. cordifolia
(Dum.) Vána by Harrison and Asakawa (1989). It is of interest to note that herbertane-type
sesquiterpenes, for example, structures based on [460], have also been
reported from M. diclados collected in Taiwan (Chau and Wu, 1987).
5.2.11 Makinoa crispata (Makinoaceae)
Makinoa crispata (Steph.) Miyake from Japan was shown by Hashimoto et al. (1989)
to contain diterpene derivatives of the sort illustrated as [466–469] (see Fig. 5.7 for
structures). More recently, Liu and Wu (1997) reported the presence of the rearranged
abietane-type diterpenoid derivative “makanin” [470] from plant material of
M. crispata collected on Taiwan. Of note was the apparent absence of any of these
compounds in the Japanese plants.
5.2.12 Brown Algae
Members of Phaeophyta, the brown algae, have been shown to accumulate, in
considerable amounts in some cases, polyphenolic compounds called phlorotannins.
These oligomeric compounds are constructed from phloroglucinol (1,3,5trihydroxybenzene)
units linked by ether and/or carbon-carbon bonds. The reader is
referred to a review of these compounds written by Ragan and Glombitza (1986).
Extensive studies of brown algae, mostly involving northern temperate taxa, have
established the important part that phlorotannins play in defending plants against
herbivory (Estes and Steinberg, 1988; Steinberg, 1984, 1985, 1986, 1988). One of
the conclusions reached was that the comparatively low level of phlorotannin production
in many northern kelps and fucoids was due to the contribution made by sea
otters in controlling the number of herbivores. In that scenario, the algae are considered
to be under lower selection pressure to produce high levels of feeding deterrent
chemicals. Estes and Steinberg (1988) suggested that the levels of phlorotannins in