The Geography of Phytochemical Races

258 6 Oceanic Islands
Fig. 6.5 Compounds 542–546, terpene derivatives from Zanthoxylum
estragole [544] and anethole [545]. These data are presented in Table 6.2. Included
in this table are data for both leaves and pericarps of the specimen collected on
Oahu, which data are included to indicate a further level of complexity in this system.
The leaves of this specimen gave the only positive test for toxicity recorded
for this species, yet the pericarp extract from this sample, with very nearly the same
composition, was nontoxic. An immediate explanation for this sort of biological
activity is evasive, although some possibilities come to mind: (1) some synergism
exists within the peculiar assemblage of compounds in the leaves; (2) the unknown
compound in the pericarp tissue somehow inhibits the activity; and (3) some other
compound(s) may be responsible for the observed differences. Whatever the explanation,
the authors point out the importance of using as large a sample as possible
to assess biological activity. It is clear that selection of a single individual of either
Z. dipetalum or Z. kauaense could have resulted in misleading results.
Compound Island
Hawaii Kauai Oahu (L) a Oahu (P) a
Limonene 2b Table 6.2 Interisland variation in volatile components of Zanthoxylem dipetalum (after Marr and
Tang, 1992)
22 – –
Estragole – – 4 14
Anethole – – 57 68
2-Undecanone 11 12 – –
Caryophyllene 45 40 33 13
Humulene 9 7 5 2
2-Tridecanone 16 6 – –
Unknown – – – 2
a L = Leaves; P = Pericarp.
b Values are percentage of compound in hexane extract (GLC).