Phytochemical Survey in Solomon Islands — Morrison 
185 
controlled-temperature hot-plate and maintained 
between 70° and 80 °C Sufficient chopped tissue 
to make a loose slurry (about 4-5 grn) was 
added to the acid and the temperature was 
maintained for 2 hours, with occasional stirring. 
The hot liquid was then filtered off and cooled. 
This gave 15-20 ml of fluid for testing. 
In the main, leaf and stem tissue was used, 
although in some cases other parts of the plant 
were available. 
2. Testing for Alkaloids 
Four drops of the acid extract were placed in 
a watchglass and 2 drops of the reagent were 
added. The contents were mixed by gentle agita- 
tion and left for 10 minutes. The amount of 
precipitate formed in each watchglass was then 
estimated visually and a rating recorded for each. 
The ratings used were as follows : 
0- no precipitate. 
1 - slight precipitate; usually requires close ex- 
amination to see. 
2- medium precipitate; readily discernible, 
although not prolific. 
3- heavy precipitate; abundant. 
4- extra-heavy precipitate; very flocculant, 
filling whole area covered by liquid. 
After some experience, it was possible to dis- 
regard those precipitates which looked peculiar. 
For example, Wagner’s reagent usually gave red 
or reddish precipitates and any other colours 
were suspect. 
The plant material was extracted and tested as 
soon as possible after removing it from its parent 
plant. The normal delay was not greater than 
48 hours, but in a few cases it was 96 hours. 
3. Extraction of Sap on ins 
A small quantity (1-2 gm) of chopped tissue 
was placed in about 25 ml of water. The mixture 
was brought to the boiling point and then 
allowed to cool for about 4 hours. The resulting 
extract was then filtered and the tissue discarded. 
4. Testing for Sap on ins 
About 10 ml of the filtered extract was shaken 
for about 30 seconds and allowed to stand un- 
disturbed. The time taken for the froth, if any, 
to disappear was noted. If the froth persisted 
after 30 minutes, this was read as "saponin posi- 
tive." 
Another 10-ml portion of filtered extract was 
made alkaline with sodium carbonate and again 
shaken. If a froth persisted after 30 minutes, 
this was considered as "positive,” and probably 
indicative of diterpene or triterpene acid. 
RESULTS 
Alkaloids 
Using the method of estimation given above, 
it is clear that a maximum score of 28 is pos- 
sible, and it was, in fact, obtained from some 
extracts. On the other hand, a score of 0 was 
not uncommon. 
To set a score above which the plant is alka- 
loid positive and below which it is alkaloid nega- 
tive is tempting, but this would simplify the 
interpretation. If a plant shows some precipitate 
in all seven reagents, then it very likely con- 
tains alkaloid, perhaps only in small quantities 
due to the season of the year or to the locality 
in which it was growing. 
Unfortunately, phosphomolybdic and phos- 
photungstic acids are not as selective for alka- 
loidal substances as could be desired. In extreme 
cases the total score obtained for a plant was 
made up from its reaction to only these two 
reagents. This clearly rates as alkaloid negative, 
because there was no precipitate formed with 
any of the other reagents. In future surveys of 
this type, these two reagents could well be 
omitted without great loss. However, in Table 1 
the precipitate scores from these two reagents 
have been included. 
In Table 1 the plants tested are arranged 
alphabetically by families. The genus and the 
species are given where known; otherwise the 
author’s collection number appears, in anticipa- 
tion that identification will ultimately be made 
at the Herbarium in Honiara. 
Names in parentheses are native names. The 
place and month of collection are also shown, 
together with the score and the number of 
reagents which produced precipitates (for ex- 
ample, 12(5) means a score of 12 derived from 
5 reagents). The native names have been taken 
from the check list by Whitmore (1964). These 
are by no means authoritative and are offered 
as a guide only. 
