Biology Reference
In-Depth Information
O
H
3
C
O
OH
O
H
O
CH
3
O
O
O
H
3
C
H
3
C
tanshinone II A (
57
)
H
3
C
O
H
3
CCH
3
O
CO
2
H
2
β
, 5-epoxy-5,10-dihydroxy-6
α
-angeloyloxy-9
β
-isobutyloxy-
germacran-8
α
, 12-olide (
56
)
O
O
OH
13-HOA (
58
)
OH
CH
3
H
3
C
H
3
C
CH
3
CH
3
H
3
C
H
3
C
H
OH
CH
3
CH
3
HO
2
C
retinoic acid (
60
)
guggulsterol (
59
)
O
CH
3
Fig. 6.10
Some naturally occurring LPS antagonists.
6.2 Initial Discovery of Ellagitannins as Immunostimulants
Polyphenol-rich folk medicines from China and Japan, including tannin-
containing decoctions, had been used for some time to treat a variety of
ailments. In 1987, Okuda, Miyamoto, and colleagues reported that
several tannins displayed tumoricidal activity against a model cancer cell
line, sarcoma-180 (Miyamoto
et al.
, 1987b). They found that the tannins'
anticancer activity was due to their ability to act as immunostimulants in
a manner reminiscent of LPS.
6.2.1 Anticancer activity
Some tannin-containing plant extracts became the focus of isolation
studies as a consequence of this promising antitumor activity. For
example, Miyamoto and co-workers initially reported that the methanol
extract from the roots of the plant
Agrimonia pilosa
Ledeb was active in
mice against several transplanted tumors (Koshiura
et al.
, 1985). The
causative agent was identified tentatively as the dimeric ellagitannin
