"The Encyclopedia of Edible Plants of North America"
by Francois Couplan, Ph.D.
Page 310:
"The bitter, aromatic fruits of P. trifoliata - E. N.Am. - have been used to replace hops for flavoring beer. They were sometimes ground, sifted and mixed with meal or flour to make bread. The root bark is tonic and stomachic. It has occasionally been used as a quinine substitute. The fruits of angustifolia (= P. baldwinii) and pallida - S.W. U.S., Mex. -can be used like those of P. trifoliata (m.a.). However, some people suffer from dermatitis after contact with the leaves of P. angustifolia (m.a.)."

Does anyone know something more about it?
EDIT 2012-01-10: Reported by hardyvermont (Tue Jan 10, 2012 5:16 am):

Quote:

P. trifoliata in this case is Ptelea trifoliata, called hoptree

Or about this:
Indian journal of Natural products and Resources, Vol 1(2), June 2010
Page 162:
The hot-water extract of P. trifoliata fruts has been used in traditional medical practice for a long time, such as in the treatment of stomach disorders.
Additionaly, the anti-inflammatory and anti-alergy actions of the fruits of P. trifoliata have also been reported."

http://nopr.niscair.res.in/bitstream/123456789/9823/1/IJNPR%201(2)%20150-167.pdf
Use copy/paste of link above to address bar in order to access document.

Never heard of it & would be scared to try it.

Laaz,
you have been to fast and I did edit of the post w/o seeing your answer.
New info is in the top post.

Now hunting article:

Anti-inflammatory activity of 21(α, β)-methylmelianodiols, novel compounds from Poncirus trifoliata Rafinesque
European Journal of Pharmacology (October 2007), 572 (2-3), pg. 239-248
H.Y. Zhou; E.M. Shin; L.Y. Guo; L.B. Zou; G.H. Xu ; S.H. Lee ; K.R. Ze; E.K. Kim ; S.S. Kang ; Y.S. Kim

Abstract and Article Outline is here:
http://www.sciencedirect.com/science/article/pii/S0014299907007819

"The fruits of Poncirus trifoliata (L.) are widely used in Oriental medicine as a remedy for allergic inflammation."

Aaaah so that's why poncirus tastes bad... it's medicine

This becomes complicated
I've read somewhere that Zhi Shi is Chinesse name for Poncirus, but that is wrong. Take this page for example:
http://www.tcmassistant.com/herbs/zhi-shi.html
"Names for Zhi Shi
Pharmaceutical: Fructus Immaturus Citri Aurantii
Botanical: Citrus aurantium L., Citrus wilsonii Tanaka, Poncirus trifoliata (L.) Raf. (Rutaceae)
Other names: Sheng Zhi Shi, Chuan Zhi Shi, Jiang Zhi Shi
Description: Immature Orange."

???

This needs a research on it's own.
Much better starting point, UNESCO project:
"International Collation of Traditional and Folk Medicine: Northeast Asia", Vol. 1, 1996., page 80.:

"
Poncirus trifoliata DC. (Rutaceae)
Gou-ju (C), Gou-Gwut (H), Karatachi (J), Taeng-ja-na-mu (K)
Fruit
Local Drug Name: Zhi-ke, Zhi-shi (C), Gou-Gwut(H), Ki-koku, Ki-jitsu (J), Ji-gak(K).
"

This will take a time...

This reminds me that a few years ago I was contacted by a researcher working in a Northern Ireland hospital. He had apparently detected some residue of poncirus in the blood of patients who had died of (I think it was) leukemia. He asked if I had any idea how this could be!

After some thought I replied that it was probably the result of some Chinese medicine these patients had tried. Chinese herbal medicine shops are certainly quite common in London - although perhaps not in Northern ireland. There are also plenty of on-line Chinese medicine shops. Personally, I wouldn't risk them until all other hope had gone.

P. trifoliata in this case is Ptelea trifoliata, called hoptree

I played a bit with hot-water extracts (HWE) of Poncirus trifoliata "Siscia" fruits this winter, results:

1) HWE of sliced full fruits
==> has taste similar to the tea of Salvia officinalis (garden sage).

1.1) Above + tea spoon of local 'instant lemon flavored drink powder'
==> has taste similar to a 'grapefruit tonic water' (refreshing drink available in stores).

2) HWE of sliced fruits with the most of rind (peel) removed
==> has taste similar to the tea of Matricaria chamomilla (camomile).

Looking forward for this season crop.

"Potential pharmacology

In vitro studies show that the fruits of Poncirus trifoliata might contribute to the treatment of mast cell-derived allergic inflammatory diseases.[3]
The chemical compounds neohesperidin and poncirin isolated from Poncirus trifoliata may be useful for the treatment of, and/or protection from, gastritis.[4]
Poncirus trifoliata extracts have been shown to possess in vitro anti-allergic, antitumor,[5][6]
anti-inflammatory and antiviral activities.[7]
Poncirus trifoliate extract could possess a wide range of beneficial activities for neurodegenerative disorders.[8]
A water extract, taken for 10 weeks, suppressed weight gain in rats.[9]"

Above + references + more:
http://en.wikipedia.org/wiki/Trifoliate_orange

More about the use of Poncirus trifoliata fruits, from already mentioned book "International Collation of Traditional and Folk Medicine: Northeast Asia":

Proccessing: Cut immature fruits and dry under the sun (J,K).
Method of Administration: Oral (decoction: extract) (H,J,K), Bathing (J).
Folk Medicinal Uses:
1) Gastritis (K).
2) Perspiration (J,K)
3) Apepsia (J,K)
4) Hernia (C,H)
5) Traumatic injury (C,H)
6) Abdominal pain (K)
7) Sputurn remedy (K)
8 ) Common cold (K)
9) Diarrhea (K)
10) Itching (K)
11) Infant beri-beri (K)
12) Neuralgia (K)
13) Contusion (K)
14) Urticaria (K)
15) Sinusitis (K)
16) Rhagadia (J)
17) Thirst (J)
18 ) Uterine prolapse (C)

Contraindication: in pregnancy. Spleen and stomach indeficiency.