On Thu, 04 Apr 2002 CA wrote:
>Fluorescein is an older name for the iron-scavenging pigment pyoverdin
> which is a yellow-green pigment.
Continuing this old thread, which I started, with new
information........to recap:
1) I was very surprised when I found an old publication
"The Mineral Requirements for Fluorescin Production", King et al,
Canadian J Research 26C, 514, 1948, as I had thought that
fluorescin/fluorescein was strictly a synthetic compound. In this
publication I found no evidence that the specific compound we call
fluorescein had actually been isolated, and its chemical identity
confirmed. (Fluorescin is readily oxidized to fluorescein)
2) I posted a question here asking if anyone could confirm
that any microbe really did biosynthesize the compound fluorescin. I
got a couple replies suggesting that the word fluorescin was formerly
used to indicate any fluorescent pigment, and not specifically the
compound we now call fluorescin.
3) Back to the lab: we have in our natural products crude
extract library 114 extracts of various Pseudomonas sp. from ~80
different isolates, some only identified to the genus level. I
selected ~25 extracts, trying to get as much diversity at the
species level as possible. After a bit of methods development to get
a reverse phase solvent system in which both fluorescin and pyoverdin
could be detected, these extracts were examined on an hplc/diode
array. In no case was fluorescin detected, but in a number of cases
a small amount of pyoverdin was detected.
So as far as I'm concerned the matter is settled: Pseudomonas
does not produce the specific chemical we call fluorescein/fluorescin,
but does produce other fluorescent compounds. Guess I should write
the editors of the Merck Index and inform them they have a small error
in entry 4196.
By the way, this was work-related, as I had been asked to
confirm the purity and identity of a series of fluorescein derivatives
being used in one of the antiviral screening labs. Being able to
resolve contaminating compounds from synthetic fluoresceins and
accurately measure the intended compound was essential. What better
challenge than to quantify it from a complex crude extract,
particularly one that has other fluorescent compounds in it?
Tom McCloud, SAIC-Frederick Cancer Research
