This is the last post, attempting to find interesting chemistry for Siromi Samarasinghe’s birthday. Although this one isn’t about smell or being stinky, it is about civet feces.
You’ve probably heard about the really expensive coffee that’s made from an animal’s dung. It’s called Kopi Luwak. Kopi for the Indonesian word for coffee and Luwak for the Asian palm civet, Paradoxurus hermaphroditus. The luwak eats the coffee berries and digests them, imparting a unique flavor to the coffee beans. The beans are retrieved and cleaned from the luwak feces.
Jumhawan et al used gas chromatography with mass spectroscopy (GC-MS) to identify metabolites that can be used to identify genuine Kopi Luwak. From the news blurb: Kopi Luwak sports higher concentrations of malic acid and citric acid, as well as a higher ratio of inositol to pyroglutamic acid.
Selection of Discriminant Markers for Authentication of Asian Palm Civet Coffee (Kopi Luwak): A Metabolomics Approach
GC uses a long coiled tube rather than the large columns, packed with a solid phase, used in liquid chromatography. The mobile phase is gas, hence the name, and the stationary phase is a thin layer of liquid or an insert sold support.
In searching for an alternate picture for this post I found that the palm civet is being exploited due to the high price for Kopi Luwak. Many civets are being caged and feed only coffee berries.
World’s most expensive coffee tainted by ‘horrific’ civet abuse
Maclura pomifera is a tree that grows throughout the US and part of southeastern Canada. It’s related to the mulberry tree although the fruit would make you think it’s citrus. The Osage Indians used it’s wood to make bows and clubs due to it’s resistance to decay and durability. It’s no surprise that modern use of the wood is for fence posts and tool handles. The tree was planted in rows in the Great Plains states to help break the wind, hence the nickname “hedge apple”. The fruit used to be placed under the bed to repel some insects.
Fruits grow to their full size (ca. 500 g) every fall, and each fruit can bear up to 300 seeds per fruit. Osage orange has traditionally been used as an insect repellent and as a home remedy for pest control. Fruit extracts and extracts of the bark, seeds, leaves, and roots, as well as the two major isoflavone constituents of the fruit, osajin and pomiferin, were reported to possess a number of biological activities. Some of the reported activities include insect repellant, antimicrobial, anti-inflammatory/antinociceptive, antitumor, cardioprotective, and cholinesterase inhibitory activities. Osage orange isoflavones, especially pomiferin, also have marked antioxidant activity and have been shown to inhibit lipid peroxidation and to reduce free radicals, reactive oxygen species, and other unstable molecules. At present, there are no osage orange-based dietary supplements available on the market, but its potential has been suggested. Biological evaluation of semisynthetic osajin and pomiferin analogues, iso-osajin and iso-pomiferin, has also been attempted by Orhan et al. Being edible by squirrels, horses, and other animals suggests that osage orange is safe. Nevertheless, the toxicities of the different extracts have not been fully established. References removed for readability
HPLC Determination of Isoflavone Levels in Osage Orange from the Midwest and Southern United States
Ketur Darji, Cristina Miglis, Ashley Wardlow, and Ehab A. Abourashed
You often hear about herbal or Ayurvedic remedies for a whole host of ailments. I won’t talk about homeopathy because that’s too easy to dismiss. Pharmacognosy is the study of medicinal compounds derived from plants. You might hear about ethnobotany and phytochemistry in descriptions of pharmacognosy. Ethnobotany is the study of plants as they relate to culture, predominantly indigenous cultures. Phytochemistry is the study of the chemistry of plants (cue elderberry joke). It’s pharmacognosy that’s used to determine if a “traditional” remedy has any scientific basis. Typically ethnobotany is used to find some candidate plants. I have a friend in this field and if I recall correctly, there was a time when western scientists would go to the jungle (for example) and take plants without working with the local government. Relationships soured and some areas are off limits. I believe most of the studies now have agreements with the local governments and indigenous people so that it’s not the new version of pillaging their gold, i.e., if a derived compound leads to a blockbuster drug, they’ll get a slice of the pie.
After a candidate plant is chosen, Maclura pomifera in this case, compounds are isolated from the bark, fruit, flower, leaves, and roots. Since this is a tree, I’m guessing the roots were not tested. Typically the compounds will be separated based on water solubility. You might know that a lot of old remedies are made with ethanol, i.e., a tincture. Then each compound is analyzed for it’s chemically properties, e.g., structure and then against a host of in vitro assays to scan for potential medicinal uses, possibly beyond what was learned from ethnobotany.
The paper referenced above (which is behind a paywall) used high pressure liquid chromatography (HPLC). Chromatography comes from the Greek chroma “color” and graphein “to write”. There are different types of chromatography but each results in a chromatograph. Its name derives from its early use in separating pigments in plants. Probably using thin layer chromatography (TLC), where a plate or piece of paper is used in a solvent. The sample is placed on one end of the plate/paper and the individual compounds separate as it travels through the solvent. This can be due to size, charge, or polarity. In HPLC, there is a mobile phase and stationary phase. Typically the stationary phase is made of special porous micron-size silica beads and is packed into a steel column. The mobile phase is typically a solvents like toluene or acetonitrile. When the mobile phase is less polar than the stationary phase it’s called normal phase liquid chromatography. When that’s reversed, i.e., the mobile phase is more polar than the stationary phase, it’s called reverse phase liquid chromatography. The reference above used reverse phase.
For a long time the effluent from HPLCs were connected to a UV-Vis (ultraviolet and visible range) spectrophotometer. Each compound has a preference for each phase (mobile or stationary). They travel through the column at different rates and they have different spectra. That’s how you get the chromatograph. In the old days, the spectrometer was tuned to a single wavelength, typically where your compound of interest has a peak. Later, with photodiode array technology, the whole spectrum for each compound was acquired, resulting in a 3D chromatograph. However, now, HPLC detectors are predominantly mass spectrometers (MS). So you get the mass of each compound as it elutes from the column.
Going back to pharmacognosy and Maclura pomifera. Two of the main compounds isolated are pomiferin and osajin . In another study pomiferin was isolated and had an inhibitory effect on the growth of 5 tumor cell types.
Pomiferin, histone deacetylase inhibitor isolated from the fruits of Maclura pomifera.
Son IH, Chung IM, Lee SI, Yang HD, Moon HI.
Bioorg Med Chem Lett. 2007 Sep 1;17(17):4753-5. Epub 2007 Jun 26.
When ScienceSunday first started, Robby Bowles and Allison Sekuler had an idea that photographers could share interesting pictures with real scientist (Robby and Allison) and the Science Sunday team could either answer a science question or add some science goodness. Sunday was chosen because we do this in our “spare” time and Sunday seemed like the best day for spare time. So the hashtag #ScienceSunday was born, followed by the page. As the popularity of the hashtag grew, more curators were added: Rajini Rao, me and then Buddhini Samarasinghe. The hashtag and page continued to grow. So we often have guest curators to help out. Unfortunately a lot of people see a trending hashtag and use it because they think that people won’t want to see their post/photo otherwise. The curators have to sift through a lot of junk to find the good stuff. So welcome Aubrey Francisco our new co-curator with some good stuff. The pictures below were from my trip to the Fox River, Silver Springs State park, yesterday. Enjoy the rest of your #ScienceSunday and don’t forget to tag one of the curators when you have a science question or some science to share.
There was a story on NPR describing a study about asymmetrical tail wagging of dogs. In 2007 Dr. Vallortigara found that a dogs tend to wag their tail to the right when they see something friendly and wag to the left when something is threatening. In 2011 Artellea et al, used a robotic dog to see how dogs would respond to a tail wagging left or right, i.e., does the tail wagging communicate fun or danger? When dogs saw the robot tail wag left, they approached without stopping. When they saw it wag to the right, they were more cautious and stopped frequently as they approached. Dr. Vallortigara followed up his previous study, this time using a video of a dog, either wagging left or right. A group of dogs watching the video had vests, which recorded their heart rate. As expected, the heart rate was normal when the tail was wagging to the right in the video and the heart rate increased (a sign of agitation) when the tail in the video was wagging to the left. The next question is how can we use this information. It should be noted how each study builds on the previous study. That’s how science works.
The image below, from Quaranta et al, 2007, shows the angle/method for determining a left or right bias tail wag. In A the tail is wagging right and in B the tail is wagging left, i.e. left and right determinations were with respect to the dog, not the observer.
EDIT for clarity.
The Tail’s The Tell: Dog Wags Can Mean Friend Or Foe
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