Sciencemadness Discussion Board

Hydrangea Blooms and PH

ssdd - 15-6-2007 at 05:51

I was sitting outside the other day looking at a Hydrangea plant we have growing.

I know that the blooms come out pink for acidic soil and blue in basic soil. (And purple for somewhere between.) I was wondering what chemical in the plant causes this? And can it be extracted at all? If so by what method?

I know that this wouldn't be a great indicator or anything but it seems interesting that plants blooms can respond to PH of the soil like this.

-ssdd

Mr. Wizard - 15-6-2007 at 11:25

I thought the Hydrangea were Blue in acid soils and Pink in alkaline. In the alkaline soil of my area, the only way to make them blue is to treat the soil with Ferrous Sulfate, which nobody has, Alum, which nobody has, or soil sulfur which will work if you are not watering the hell out of the plants to keep them from drying out in the heat. In short it's tough to get results unless they are inside and watered with distilled water.

Other vegetable dyes do change color too. I think red cabbage is blue when basic and red when acid. Other fruit juices display similar color changes. It would be interesting to see a pH chart made of vegetable extracts. Maybe I should UTFSE before I mention it? ;)

DerAlte - 15-6-2007 at 21:43

WRT the color of hydrangeas, Mr. Wizard is right. Opposite to litmus. I have some potted ones now, all pink (the color my wife likes). I have previously turned them blue (my favorite) with acidity from vinegar before blooming. To know why the colors are so, Google it.

Regards,

DerAlte

Pyridinium - 18-6-2007 at 00:01

I have a citation (just the ref., not the paper) that looks interesting re: hydrangea colors:

Bunyard, E.A. "The Effect of Salts Upon Pigments", Gard. Chron., London, XLVI: 97-98 (1909).

I don't even know where somebody would find this journal, or what the full name is (Gardening Chronicles?). According to the very brief notes I have, the presence of lead salts affects the color of the hydrangeas (red). This is the opposite of the usual coloration of lead on anthocyanins (bluish).

Among my other projects with anthocyanins I might just have to get around to growing lead-treated hydrangeas to see if this is true.

I see that the pH effects seem to be backwards as well (normally acid = red, alkaline = purple to teal).

Not sure what the specific anthocyanins are. A lot of stuff on the web lists "hydrangin", but this is a coumarin derivative. As far as I can tell, this isn't what gives hydrangea its color.

A lot of links on the web state that hydrangin is a "cyanogenic glucoside", but hydrangin itself isn't even a glucoside, and it isn't cyanogenic. It's a coumarin derivative, and it has no nitrogen. Skimmin is the actual glucoside of hydrangin. Also not cyanogenic. Either there are two different "hydrangins" or something is wrong with the net definitions.

not_important - 18-6-2007 at 01:13

Quote:
Originally posted by Pyridinium...
Not sure what the specific anthocyanins are. A lot of stuff on the web lists "hydrangin", but this is a coumarin derivative. As far as I can tell, this isn't what gives hydrangea its color.



Hydrangin is extracted from roots and rhizomes, not from the flowers.

Pyridinium - 18-6-2007 at 08:57

Quote:
Originally posted by not_important
Hydrangin is extracted from roots and rhizomes, not from the flowers.


That's nice, but what's the actual coloring matter in the flowers? Do you know the name of it?

EDIT: Nevermind, it's the 3-glucoside of delphinidin.

Taking a look at
http://www.botanical-online.com/alcaloideshortensiaangles.ht...
it mentions hydrangin and then says "Active parts: The whole plant."

At http://www.ces.ncsu.edu/depts/hort/consumer/poison/Hydrasp.h...
it says bark, leaves and flower buds are the poisonous parts.


Nearly every web source says hydrangin (umbelliferone) is a cyanogenic glucoside. They must be confusing it with something else. They keep regurgitating the same 1 or 2 primary sources, vague to begin with. There is nothing in the structure that suggests HCN on hydrolysis. Its glucoside, skimmin, also has no CN group.

EDIT 2: Oh, I also found out why the pH behavior seems to be reversed... it's because of Al complexing, with the Al being mobilized more at acidic pH.

[Edited on 18-6-2007 by Pyridinium]

not_important - 18-6-2007 at 15:27

You might also want to look at these

[Edited on 18-6-2007 by not_important]

Attachment: Hydrangea Flower Color M350404038e.pdf (252kB)
This file has been downloaded 753 times

not_important - 18-6-2007 at 15:30

argh - wrong bbs software

Attachment: Hydrangea Flower Color 98005.pdf (306kB)
This file has been downloaded 852 times

Ozone - 18-6-2007 at 16:03

I have posted the original paper here (which is cited frequently in the superficial literature). I do not read in it, so far, any indication that the isolated compound was a cyanogenic glycoside (it was treated with HCl, and I am sure it would have been noted and tested via prussian blue) like Laetrile (which yields HCN on acidic hydrolysis).

It also appears that Al in the soil is required and the pH determines the amount of free Al that can be taken up. I know that most anthocyanines and bioflavanoids are also very sensitive to Fe (complexes which serve as nice indicators).

Any references to Al or Fe with regards to color at various pH?

Cheers,

O3

Attachment: hydrangin_01.pdf (30kB)
This file has been downloaded 752 times

12AX7 - 18-6-2007 at 16:24

Tangentially, calmagite complexes with Ca and Mg ions, giving the same color change (pink when complexed, blue when free, as I recall).

Tim

Ozone - 18-6-2007 at 19:40

Not exactly,

A bit about hardness (water) testing is given here:

http://chemmovies.unl.edu/chemistry/smallscale/SS051c.html

cheers,

O3

Pyridinium - 18-6-2007 at 21:18

Quote:
Originally posted by Ozone
I have posted the original paper here (which is cited frequently in the superficial literature). I do not read in it, so far, any indication that the isolated compound was a cyanogenic glycoside

...

Any references to Al or Fe with regards to color at various pH?


This is puzzling. I haven't been able to find any picture of the structure of this "cyanogenic glucoside" that all those web sites are talking about. One or two of them mentioned a similarity to amygdalin, but you can tell from looking at the amygdalin structure that it has the potential to give HCN. Of course, so does cyanocobalamin, but it's used in such small amounts...

I wish we could get that paper from 1909, I bet it would have some info on the pH dependency of Al or Fe colors w/ anthocyanins.

logp - 19-6-2007 at 09:18

Quote:
Originally posted by Mr. Wizard
I thought the Hydrangea were Blue in acid soils and Pink in alkaline. In the alkaline soil of my area, the only way to make them blue is to treat the soil with Ferrous Sulfate, which nobody has, Alum, which nobody has, or soil sulfur which will work if you are not watering the hell out of the plants to keep them from drying out in the heat.)


My grandmother always burried lumps of rusty iron around her's to make them change colour. Unfortunatly, I can't remember wether she did this to make them blue or pink, which is frustrating.

Chemistry29 - 19-6-2007 at 09:21

Apparently sulfur and rust nails (iron oxide) can change their color

(i got my account fixed i am going back to chemkid)

[Edited on 21-6-2007 by Chemistry29]

ssdd - 21-6-2007 at 05:51

Thanks

I just got home from a week away so I'll have to read everything you guys posted.

Sorry, didn't realize I mixed those up. :o

Anyone know why rust and sulfur change the colors of the flowers. (perhaps after I read some of the pdf's I'll find out.)

-ssdd

UnintentionalChaos - 21-6-2007 at 23:15

I thought that ammonium and aluminum sulfate were the standards for altering the color of hydrangea blooms and for acidifying the soil for blueberries for that matter. Both are fairly easy to get a hold of at garden centers and their effectiveness is supported by the above discussion. I know it's kind of off-topic, but I am working for the summer at a garden center and know my way around plants quite well (gardening since I was a little kid).

ssdd - 22-6-2007 at 02:55

What I am still having a hard time finding, and perhaps I'm just missing it, is: I see the chemical here that is causing the color changes, but how do I extract it? (If it can be done?)

I tried taking a few blooms and running them through the blender for 15 seconds or so to get a pink solution of very fine Hydrangea chunks. It was a purple in color. I added some to vinegar hoping to see blue but no luck!

Any Ideas?

-ssdd

Pyridinium - 22-6-2007 at 17:53

Quote:
Originally posted by ssdd
What I am still having a hard time finding, and perhaps I'm just missing it, is: I see the chemical here that is causing the color changes, but how do I extract it? (If it can be done?)

I tried taking a few blooms and running them through the blender for 15 seconds or so to get a pink solution of very fine Hydrangea chunks. It was a purple in color. I added some to vinegar hoping to see blue but no luck!

Any Ideas?

-ssdd


What you need is a good procedure to extract the anthocyanin(s), which as I said is probably delphinidin. We had a recent thread on the extraction for another one, can't remember the link offhand, but do a search. The key is getting the right mix of alcohol and water (anywhere from 20-95% EtOH, though some use MeOH with better results) with about 1-2% HCl in it.

ssdd - 24-6-2007 at 03:30

I was able to find what you were talking about, I am going to try it right now. (You know your a geek when your running chemistry at 730 am... :P )

Thanks I'll post my results.

-ssdd

Ozone - 24-6-2007 at 18:12

To me, the indicator is, in fact, a metal complex. The ligand itself, like caffeic acid, has no significant indicator value. The Fe complex, though, is a very nice universal indicator. The soil pH likely determines which (and how much) metal ions are free for uptake into the plant.

Try adding a little FeCl3 (10%, a drop or two) to some of your extract.

Attached is a photo I made while titrating caffeic acid/Fe.

Cheers,

O3

CaFe pH curve_01small.jpg - 92kB