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FROM THE ARCHIVES: Herbs And Spices – A Family Affair

By Carl Price and Ellen Reardon, first published in Let’s Talk Plants! January 2009, No. 172. Republished January 2024.

WiX stock photo of herbs and spices.

Herb and Spices: A Family Affair

Herbs and spices are popular in our gardens, but what makes them so attractive to us humans? They may or may not be visually attractive; they are not necessarily rich in nutrients; and they may or may not have medicinal value. A simple reason for their ubiquity in our kitchens is their flavor and/or aroma. Classes of substances known as secondary metabolites are typically responsible for flavors and aromas in plants. The term refers to substances that are not part of essential, primary processes such as uptake of nutrients, photosynthesis, transpiration, etc. Whereas the machinery of these primary processes is highly conserved across the plant kingdom, secondary products vary enormously, and their chemical structures display evidence of plants being the most ingenious chemists in the world. Flavors and aromas are typically similar within genera and families but are rarely duplicated among families.

Let’s look at some examples:

Black pepper, Piper niger

WiX stock photo of black pepper.

The genus Piper contains over 1400 species, of which half a dozen are widely used in cooking. The most familiar to us is black pepper, P. niger. The spice comes as dried fruits (known as “peppercorns”) of the plant, but note that we call it “black” only because that is the most common form. Depending on harvest time and processing, the dried fruits can also be white, green, pink, or red. The pungency of black pepper is due mainly to piperine, an analog of alkaloids, while monoterpenes, such as sabinene in pepper oil, are responsible for its aroma.

Chili pepper, Capsicum spp.

WiX stock photo of chili peppers.

The genus Capsicum includes about 30 species, of which half a dozen are cultivated; C. annuum is far and away the most abundant in the United States and Europe. Other species that a widely cultivated include C. pubescens, C. baccatum, C. chinense, and C. frutescens. There is a single set of compounds responsible for pungency in chili peppers: capsaicin and a small group of derivatives, capsacinoids. What’s more, these substances are found only in the genus Capsicum. We should also note that there are many varieties of C. annuum that we call “sweet” or “bell” peppers. They are not pungent because they have little or no capsaicin. It turns out that capsaicin is encoded by a single gene, and sweet peppers contain an inactive, recessive version of this gene.

Other herbs and spices

WiX stock photo of Rosemary.

If we had additional space, we could explore the distinctive properties of many more herbs and spices. Rosemary, Rosmarinus officinalis, for example, is a popular herb in Mediterranean kitchens, but it’s more than an herb or spice. Consider the pleasure of running one’s hand up its stem! Chives, Allium schoenoprasum, another example, are very different from the two “peppers.” A member of the Allium family, chives share a similar set of components with garlic and onion, which are other members of the family, but their flavor and odor are quite distinctive.

A remarkable reference

In trying to understand the essential elements of herbs and spices, we searched Google, which of course has an infinite array of references. One of the most remarkable is Gernot Katzer’s Spice Pages Welcome to Gernot Katzer's Spice Pages ( Katzer presents detailed information on more than 100 herbs and spices, covering everything from the kitchen to the botany and chemistry labs. The English version, cited above, has some minor translation problems, but he is forgiven.


WiX stock photo.

Members Carl Price and Ellen Reardon are retired from Rutgers University, where they conducted research on the molecular biology of plastids and served as editors of

journals in their field.



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