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Science Talk

What's In A Rose: Ethnobotany and the Search for Useful Plants

In this episode, ethnobotanist Nat Bletter talks about his field and his recent article about the new plant family Simulacraceae--the phony plants. Plus we'll test your knowledge of some recent science in the news. Websites related to this episode include;;;

September 19, 2007 -- What's In a Rose?: Ethnobotany and the Search for Useful Plants

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Steve: Welcome to Science Talk, the weekly podcast of Scientific American for the seven days starting September 19th. I am Steve Mirsky. This week on the podcast: We'll look into the fascinating world of ethnobotany with Nat Bletter. Plus, we'll test your knowledge about some recent science in the news. Nat Bletter is finishing up his doctorate at the City University of New York and through the International Plant Science Center at the New York Botanical Garden. We first got in touch a few months ago, when he sent me a recent scholarly publication, which we'll talk about, and this past Sunday, he led a walk through Central Park in search of edible plants, you know, in case you are stranded there and can't make it to a hot dog stand. Anyway, we walked and then we talked.

Steve: I'm sitting in Central Park with Nat Bletter. Nat is an ethnobotanist. Why don't you start off by explaining what ethnobotany is and what you do?

Bletter: Okay. Thanks for having me on Steve. Ethnobotany is basically defined as the relationship of plants and people. So it can be more specifically the study of plants that people use for food, for clothing, for medicine, for construction, for ceremony, for decoration—any useful plant you might talk about and I've specifically focused on the medicinal plants and the edible plants and with my research on chocolate, I guess, the psychoactive plants too, you could say.

Steve: You define chocolate as a psychoactive plant?

Bletter: Oh definitely! Yeah!

Steve: How is that?

Bletter: I just wrote a chapter on the traditional uses of cocoa all throughout the Americas and did a review of the chemistry of the plant, and I found that there is about 13 different neurotransmitter or neurotransmitter analogs in chocolate, including dopamine analogs or precursors, serotonin, tryptamine, cannabinoids. So, it's along with the phenylethylamines and the caffeine and theobromine that are traditionally discussed, and they are all there in very small amounts, but it's got to be with the combination of all these different neurotransmitters—that's I think why it has such a profound effect on people.

Steve: And also it's delicious.

Bletter: That too, yes.

Steve: So you travel around the world as part of your research. Where do you go and what do you there?

Bletter: My main research for my PhD is in Peru, in the Peruvian Amazon, and in Mali in West Africa, and I am looking at the medicinal plants used there in traditional societies and indigenous groups for parasitic diseases like malaria, autoimmune diseases like diabetes and eczema and uterine fibroids, and trying to see if there is an overlap, so that if people in Peru and Mali are using a similar species to treat the same disease, that's a good bet that it is something effective, because they have independently found something useful, you know? There is probably no chance or very little chance that someone in Peru has talked to someone in Mali about, "Oh, you should use this plant for malaria", because they are so separated and they are not going to have the same exact species. But we can look at the evolutionary relations of the plants and say, "Oh, they are using something pretty close to both to treat malaria, so lets take those plants into the lab first before any of the other ones because they are most likely to be effective."

Steve: You'll look for an active ingredient in the plants, some kind of active compound that both plants produce—might it be the same compound or maybe it's a related compound?

Bletter: It could be and we haven't gotten that far yet. I mean, if there is existing literature studies looking at those plants where they found active compound[s], I definitely will use that, but first I am trying to show that there is a pattern—that if you do some math and try to synthesize all this information about the different plants being used in different cultures for different diseases, and using the evolutionary relationships of the plants, the cultures and the diseases to sort of merge it all together and have these equations spit out a sort of potential efficacy—our best guess of what the efficacy of this plant is. So now I am trying to test on the crude extracts of the plants, what the efficacy is, and then if something turns out to be really effective, then we would go on and try to narrow it down to one or a group of compounds in the plants.

Steve: We were just on this walk through Central Park together, where you were pointing out what some of the edible plants are in the park, and you noted that in your ethnobotanical research, you are not only interested in the plant, you are interested in specifically how the plant is used. For example, if an indigenous person uses the plant only when it grows next to some other plant. So why don't you talk a little about that? How the context is such an important part of what's in the plant and what you can possibly get out of the plant.

Bletter: Yeah! It's becoming clear and clearer as people look at different stages of the plant's growth and in different habitats growing next to other plants that the stressors in the environment can really change the chemistry; because most of the medicinal compounds in the plants are what are called secondary compounds, so they are not things essential to the metabolism of the plant like sugar and water and ATP for energy and DNA. There are these other compounds that the plants, it needs extra energy. It will only make them when it really needs them. And so when it's in a stressful environment, it definitely needs them to protect itself from attack by pests, and, you know, if its water stressed or if there is some plant growing next to it that's putting out toxic chemicals—there is lot of plants like walnuts, or eucalyptus too, in response to those compounds, it will produce other compounds that turn out to be good antioxidants for humans too and that's why they work as effective medicines.

Steve: So if you sequence the genome of the plant, you might find the gene for [a] particular compound, but that gene wouldn't get expressed unless the situation—the stressors—were affecting the plant in that particular situation and then that gene gets turned on.

Bletter: Exactly! Yeah! There is something that flips a switch and it's usually not just one gene either, because most of these secondary compounds that make effective medicines are not just simple proteins that can be made by one gene; they are actually simpler molecules, but they have to be made by a whole pathway that has, you know, enzymes that are snipping here and adding on parts of the compound there, so that whole pathway has to get turned on and all these pathways can go in different directions. So, for instance, in the opium poppy, there is one pathway that makes the heroin compound, the opium compound, and there is other ones that makes the codeine compound and so [on] in different stress conditions.

Steve: Let's take a little break, while the helicopter figures out where it wants to go.

Male voice: Science Video News, now at; easy to view and updated three times a day. Video News, just a click away at

Steve: Okay the chopper seems to have passed by. So what you were saying was there are multiple pathways. Under one set of conditions, you might get the opium and under another you might get codeine.

Bletter: Yeah! So, yeah, depending on the stress they found, there is one study, that was in New Zealand or Australia, where they grew the opium poppy in different conditions, under different stress levels, and they found that in certain cases it made more of the codeine and in other cases, it made more of the opium. So if they want to grow it for pharmaceutical production, it turned out that they had to intentionally stress the plant out and when indigenous people are saying, "I pick it from this side of the mountain, where it is growing next to this tree", they are doing effectively the same thing.

Steve: If a pharmaceutical company wants to harvest these bio molecules, they are going to be in much better shape if they have an ethnobotanist along to really analyze the context of the use of the plant, the entire plant, not just to search for active ingredients.

Bletter: Exactly! And there is[was] a big push in the 1990s of pharmaceutical companies trying to join up with ethnobotanists and look for medicinal plants, but I think they are always trying to do it as quick as possible, so they didn't always pay attention to these things. And, you know, often they would just send, you know a pharmacologist down to collect these plants, and so they wouldn't collect exactly the right one in the right condition. And then [when] they [would] take [it] into [the] lab and tested [it] there, it wouldn't work, because it didn't; it was making the secondary compounds when they harvested it and there is even cases of, you know, they say they use the root, but people don't want to bother gathering the roots, they just get the leaves instead and these parts of the plants make completely different compounds as well. So yeah, you have to spend some more time doing interviews and asking exactly how it is used, how it is prepared, because often they are detoxifying the plants or they are making mixtures of the plants, so and not[that's] something that's really hard for western medicines to deal with. You know, western medicines makes one compound from one plant that you know will cure cancer, but it might be this combination of 50 different compounds from 10 different plants that when you mix together actually do the same combination. And we are starting to realize that you have to pay attention to the synergy of the different compounds. And that's part of my research is to try to—in addition to linking these plants from different continents—also looking at mixtures of different plants and saying well, ‘"Do these, you know, groups of species always show up together in conjunction and mixtures?"And it's becoming more and more apparent that in more and more cases where this turns out to be effective. For instance in Mahonia or Oregon grape—it's a plant from the Pacific Northwest—there is one compound called hydnocarpin that will kill [a] certain type of bacteria, but the bacteria develops a resistance where it evolves this pump to remove the hydnocarpinfrom its cells and it's no longer toxic; and then it turns out that the Oregon grape also has this other compound called berberine which stops that pump from working, so it's only in combination [that] these two compounds in that plant will actually still kill the bacteria. So if, you know, a pharmacologist that come[s] along and say[s], "okay we are just going to take hydnocarpin and we are going to give that to people, it will cure them of their strep throat"or whatever; you know, after, you know, a year of use, that most of the bacteria would develop resistance. But if we had given those two compounds or even the whole plant together with whatever other auxiliary compounds there might be, it would take much, much longer for resistance to develop. And this is becoming really important in malaria treatment, because with malaria medicines, resistance develops incredibly fast, and so every five years, we have to find a new malaria medicine, that is, mefloquine becomes ineffective and chloroquine.And I just had a friend come back from Ghana, who is taking Malarone and she still got malaria. So this is becoming a bigger and bigger problem, and there is one plant I think I have mentioned on the walk, Sweet Annie or Qing Hao; it's a Chinese plant that's being used—it has been used traditionally to treat malaria and fevers—and they extract a compound called artemisinin from that which they are trying to use more and more in Africa. As resistance develops, it's very expensive right now, so it's hard for these poor African countries to use it. But in cases where they are using it, they are already starting to see resistance develop and they are realizing, "Oh, we should use all ten of the compounds that were found in artemisinin that had some efficacy against malaria". They only took the one that had the most efficacy, but there are these other minor compounds; if you kept all those in there, it would take much, much longer for the malarial parasite to develop resistance to all the mechanisms in those compounds.

Steve: Really interesting. Let us segue. I want to spend a couple of minutes talking about a really fun article that you coauthored that appeared in, was it the Journal of Ethnobotany?

Bletter: It was Ethnobotany Research and Applications.

Steve: Ethnobotany Research and Applications—why don't you just talk about the paper?

Bletter: (laughs) All right. This is a little comic relief we did at a ethnobotany conferences, the society of economic botany.

Steve: And then the paper came out in the April 1st issue of right ...

Bletter: So we hope that people would catch on fairly quick. It was on a newly discovered or newly described plant family and called this Simulacraceae, so all that [the] plant families end in "-aceae"something—so the legumes and beans are fabacea. So it's just, [we] took the word simulacrum for Artificae and we turned that into a family name. So we described the plastic plants that you might see at your dentist; the glass flowers that they have up at the Harvard Botanical Museum; the metal plants that you might see in your local mall; fabric plants that you might see down at your local Chinese restaurant; and we applied traditional botanical description to them including the Latin description. In this case, we did it in Pig Latin, however.

Steve: (laughs) Pig Latin, that's right. So what did you find altogether—I mean, the family is [a] fairly high taxonomic category, so what do you—[youthen] found 17 [genus,]genre was it?

Bletter: Exactly!

Steve: And how many species?

Bletter: So far, in our arduous research, we've found about 86 species, but you know everyday we find more. They are all over the place, and I'm really shocked that this family hasn't been described before.

Steve: And why don't you give us just some more examples. You know, you talked about the woven flowers or the metal plants, but why don't you talk about what you have actually named some of the individual species.

Bletter: All right. I'll have to definitely credit my co-authors—Kurt Reynertson, and who is a classmate of mine at C.U.N.Y., and Julie Velasquez Runk who was at Yale at the time there. They are also traveling all other [over the] places and finding specimens in Thailand and in Panama and looking for these hot spots as they call them of the "Simulacraceae."

Steve: So the wax fruit on grandma's table. That can answer it.

Bletter: Yeah! That is the wax fruit. What do we call that?

Steve: That was "Paraffinia" I think...

Bletter: "Paraffinius"—exactly, and there was some other rarer genre. There are the balloon-shaped flowers that we called "Hotairia,"I think. There is the one from Thailand from the, it is like, there is a restaurant there called Cabbages and Condoms that was sponsored by the Office of Sexual Health or something like AIDS awareness and they had a genus they called "Prophylactica" which are flowers made out of condoms; and there was, let us see what else… There is the "Conglomeratium," the cement plants, so several of those in Laos. There is the (unclear 18:03), the glowing and light up plants; there is"Plasticus" that was definitely the first genus that we found in Hawaii way back in 2001, and that was when we first started our research.

Steve: These were like just plastic ferns you see in the hotel lobby or something.

Bletter: I think it was a plastic orchid. It was the first one we described. There was "Textileria," the fabric ones, there is "Papyroidia," the paper ones—yeah, they go on.

Steve: One of the great things is the world famous collection at Harvard of the glass flowers; I[a]s you know there are about 600 species I think maybe of the glass flowers represented at the Harvard museum those all count as one genus in your artificial plant collection.

Bletter: Right! Exactly! So that is the Silicus genus and those are truly amazing, and I recommend anyone who is up in [the] Boston area to visit the Harvard Natural History Museum, and I think, they are made by Bulgarian or Hungarian brothers in the early 1900[s], and theye are amazing reproductions; I mean, if you did not let a botanist touch them and you put them next to the same species of living plant, I bet that a lot of them could not tell the difference because they are down to the minutest part; they are incredibly accurate.

Steve: Yeah! I have seen them there. They really are amazing. In fact we did an article on them in Scientific American and I will check to see when that appeared, so that people can look for it. Nat thanks very much, great to talk to you.

Bletter: Thanks so much for having me on Steve. It was [a] great time.

Steve: For more on Nat Bletter and ethnobotany just Google "Nat Bletter"—n-a-t-b-l-e-t-t-e-r—[there] is [a] very interesting link in his profile page to an entry on creating talking books for ethnobotanical field research; you might want to look at that, and to find Nat's paper on fake plants go to; that is You will see photos there and find a link to the full paper; and to read the Scientific American article on the Harvard glass flowers—800 species by the way—just go to

Now it's time to play TOTALL…….Y BOGUS. Here are four science stories; only three are true. See if you know which story is TOTALL…….Y BOGUS.

Story number 1: A new wildlife identification book is coming out, the field guide to household bugs.

Story number 2: Speaking of insects, Cyprian honeybees kill their enemy the oriental hornet by mobbing it and frying it with their collective body heat.

Story number 3: British scientists have developed skis that wax themselves.

And story number 4: Variations in a single gene can determine whether you perceive male sweat as odorless or smelling like vanilla or like urine.

Time is up.

Story number 1 is true. A Field Guide to Household Bugs features info and photos of your favorite silverfish, dust mites and other insects you probably don't know or[are] living with or even on you. The authors note, for example, that if you have used a pillow for couple of years, 10 percent of its weight at this point may be dead dust mites and their detritus. That factoid may sell more pillows than books.

Story number 4 is true. Male sweat can smell good or bad to you based on variations in just one of your genes that codes for an odor receptor. The finding appeared in the journal Nature. For more, check out Nikhil Swaminathan's September 18th article on the SciAm Web site called "The Scent of a Man".

And story number 3 is true. British scientists have indeed created skis that wax themselves. And internal network of tiny tubes—that's a series of tubes—sends a constant stream of wax to the ski surface. For more check out the September 13th episode of the daily SciAm podcast, 60-Second Science.

All of which means that story number 2, about Cyprian honeybees overheating the oriental hornet to death is TOTALL…….Y BOGUS, Because what they actually do is, swarm the hornet and smother it to death. That is according to research published last week in the journal Current Biology. The honeybees sting some enemies, but others have a hard cuticle that the stingers can't get through, so the bees mob most of them and cook them to death with their collective body heat, but the hornet is more heat tolerant, so the ball of bees smothers it.

Well that's it for this edition of the weekly SciAm podcast. Check out numerous features at our Web site including the blog, "Ask the Experts", and the latest science news, all at; and you can write to us at For Science Talk, the weekly podcast of Scientific American, I am Steve Mirsky. Thanks for clicking on us.

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