PLANTS AND PEOPLE

Spices, Herbs, and Perfumes

ESSENTIAL OR VOLATILE OILS - numerous chemical compounds are produced by plants, often in specialized secretory cells, epidermal cells of trichomes (see overview of these for the Lamiaceae), 'glands' (secretory structures) or cavities that are located on all plant structures. The compounds produced, usually terpenes (see text Fig. 8.2), must be small enough (molecular weight less than 300/400) to move through the air from the source to the top of the human nasal canal and the mucous layer covering smell receptor cells (see text, Box 8-1) and configured is such a way that they will bind to receptor sites thereby eliciting an olfactory response. The plant must budget energy to physiological paths that produce these molecules and the associated secretory structures. WHY?

It is evident that evolution does not always proceed in the most efficent manner. The current expression of a given lineage carries a mosaic of features in terms of adaptative significance and phyletic history. Some structural and biochemical elements represent movement toward or away from adaptive 'goals' or 'peaks'. Thus, there can be a 'vestigial' interpretation for some features. There is also a structural/biochemical 'momentum', termed canalization that allows features to persist despite weak, negative selective pressures because they are deeply bound into the system and 'undoing' difficult. Also, some features, both structural and biochemical, can exist in a neutral selection environment and thereby represent a more or less 'random' element of the genome. So, its possible that a biological foundation for these plant products is simply not associated with a functional or phyletic rationale but, given the importance of biochemical diversity in angiosperms, it is reasonbable to assume that an adaptive foundation is present.

One fairly obvious adaptive rationale for the production of volatile oils on reproductive structures is that applied to the modification of leaves to form the corolla, i.e., an animal-related adaptation that centers on olfactory or chemical, as opposed to visual, attraction. It appears that, as is the case with the corolla in terms of color and form, the animal world carries a common 'aesthetic' standard in that plant attractants, both visual and chemical, have evolved as a response to selective pressure imposed, in most cases, by arthropods. Our appreciation of these floral products, as indicated by modern commercial activities dealing with ornamentals, spices, and perfumes, suggests that our mammalian aesthetic 'ideal' is comparable to that of the insects. This commonality also suggests that animal mechanisms for sensing taste and smell are ancient and basal in terms of the animal lineage. At any rate, the biological basis for those volatiles produced by angiosperms on their reproductive structures is fairly straightforward.

Volatile or 'essential' oils found in plant stems, leaves, or roots (Sassafras albidum Lauraceae - root beer flavor) could have a tangential reproductive 'attraction' function - but probably more often represent sequestered waste products or - more likely - a 'repellent' function with regard to animals (mostly insects), other plants (ALLELOPATHY), fungi, or the microbial world. Thus, as is the case for many toxic compounds that we use as drugs many volatile compounds present in the vegetative plant are produced as defense against predators and pathogens and, as a result, human usage - especially in high doses - can produced unwanted results (sassafras extract - banned in Europe due to association with liver cancer, oil used there for killing lice)

Spice vs. Herb:

Herb - botanical term - not woody, 'applied' term means the same, i.e., plant material used for scent and flavor that is taken from  - usually - fresh, green tissue - typically associated with plants or TEMPERATE origin

Spice - non-botanical - applied to dried bark, roots, seeds, fruits, and flower parts that are ususlly ground or grated and used for their scents and flavors, typically from TROPICAL parts of the world

The average American consumes ca. 1 kg (2 lbs) or herbs and spices annually - we taken spice availability for granted - BUT only possible due to the modern international transportation network (temperate/tropcial, west vs. east) which was not in place during ancient times.

Ancient uses of these plants was more extensive and critical - helped preserve food (hops), cover flavors of spoilage (no refrigeration), make dull meals more interesting - also religious/mystical (herbals) ceremonies and embalming.

Spices used by the Egyptians for embalming were not native to Egypt - demand led to development of trade routes throughout the Mediterranean basin and Asia by 3400 BP - this was expanded by the Greeks (Theophrastus - ca. 2000 BP).

This trade was more fully developed by the Romans with routes expanded by them throughout the near east, Asia, and Europe - Europe cut off during the 'Dark Ages' (641-1096 AD) - and re-developed after the Crusades - Cities lying between eastern centers of spices production and the European center of demand became economically active and rich - Venice, Genoa - this helped foster the cultural rebirth known as the Renaissance. The search for spices to further develop this market produced the age of exploration with economic/political competition among European players (Portuguese, Dutch, British). Thus, the search for these plant products and subsequent economic development played a significant role in the development of European culture and Old World history in general.

Black Pepper:  Piper nigrum - Piperaceae 

Big 'Spice and Herb' families: Lamiaceae (258/6970 -Labiatae) and Apiaceae (365/2800 - Umbelliferae)

Both large families distributed globally with centers of diversity in the Mediterranean basin - both producers of distinctive and varying volatiles via specialized structures - and both with a suite of distinctive structural features, both vegetative and reproductive - both with a long association with humans (herbals) and many taxa in the ethnoflora.

Also Brassicaceae: (native European and used during the dark ages when others were not available:

 Brassica nigra/juncea  (black/brown) and Sinapis alba - mustard - taken from mixture of seed from each of the species (yellow = mostly Sinapis (British/American), darker [Northern European - 'grey poupon'] = more nigra - different mustard oils (sulphur-containing glucosinolates), different flavor.

Armoracia rusticana - Horseradish - one the the few elements of the Old World ethnoflora originating in northern Europe with subsequent disperal southward (most show the reverse pattern) - encountered most commonly in modern North America as the 'hot' component of the red sauce in a 'shrimp cocktail'. 'Heat' produced by the glycoside sinigrin which, when dissolved in water, forms the mustard oil. 

Gerard (1597), (see ref.) who describes it under the name of Raphanus rusticanus, states that it occurs wild in several parts of
England, and after referring to its medicinal uses, goes on to say:

     'the Horse Radish stamped with a little vinegar put thereto, is commonly used among the Germans for sauce to eate fish with and such like meates as we do mustarde,'

showing that the custom was unfamiliar to his countrymen, with whom the root had not yet passed from a drug to a condiment. He
mentions this plant as an illustration of the old idea of 'Antipathies,' saying:

     'Divers thinke that this Horse Radish is an enimie to Vines, and that the hatred between them is so great, that if the rootes heerof be planted neere to the vine, it bendeth backward from it as not willing to have fellowship with it.'

(this, perhaps, one of the first references to allelopathy)

Also, Clove Oil (Syzygium aromaticum - Myrtaceae - also, Eucalyptus) - known from China at 4th century BC - endemic to 'spice islands' - one of the few botanical resources derived from a flower bud.

New World Spices - ALLSPICE - Pimenta dioica (Myrtaceae) - also; Sassafras albidum (Lauraceae)

Red Pepper - Capsicum annuum (Chili), C. frutescens (Tabasco) - SOLANACEAE - spice for bland (maize, beans, squash) vegetarian diet of native americans - species in North and South America - 'hot' compound - CAPSAICIN - is concentrated on the inside of the pericarp at the point of seed attachment. Early transported to Europe - PAPRIKA - also PIMENTO [little red thing in olives - is taken from the pericarp of Capsicum fruits - edible fruits [both hot and not] are usually C. annuum.

VANILLA - Vanilla planifolia - ORCHIDACEAE - only non-ornamental crop from this huge family - perennial vines of Central America - derived from 'fermentation' of of immature fruits - hand pollinated - takes 9 months for the ovary to develop - goes through a long process of 'ripening' to produce VANILLIN [2nd to saffron in expense] - like chocolate, originally used by native Mexicans without sugar. 


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15 Apr 2010