Distribution of miliacin (olean-18-en-3β-ol methyl ether) and related compounds in broomcorn millet (Panicum miliaceum) and other reputed sources: Implications for the use of sedimentary miliacin as a tracer of millet

Abstract

bution of miliacin (olean-18-en-3β-ol methyl ether) and related compounds in broomcorn millet (Panicum miliaceum) and other reputed sources: Implications for the use of sedimentary miliacin as a tracer of millet. Organic Geochemistry, Elsevier, 2013Elsevier, , 63, pp.48-55. <10.1016Elsevier, /j.orggeochem.2013 Miliacin biosynthesis has been proposed for other Panicum species, Setaria italica (Italian or foxtail millet), Pennisetum sp., and Chaetomium olivaceum (an olive green mold). We found miliacin concentrations in seeds of different varieties of P. miliaceum to be similarly high (with trace amounts of β-and α-amyrin methyl ethers). It was absent from hulls and roots, and nominally present in leaves and stems. The transfer of miliacin from plant to sediments is therefore mostly from seeds. Miliacin was abundant (often with larger amounts of β-and α-amyrin methyl ethers) in all other Panicum species studied but only in some species of the genus Pennisetum and absent in * Corresponding author e-mail address: jeremy.jacob@univ-orleans.fr 2 Setaria italica. Neither C. olivaceum nor its growth medium (rice) showed any trace of miliacin.Our results of no miliacin from S. italica and C. olivaceum , high miliacin concentrations in seed of P. miliaceum relative to other PTMEs and to other grasses, and considering the high biomass that cultivated broomcorn millet has relative to other potential plant sources, support the use of sedimentary records of miliacin in some contexts, to track past millet agricultural dynamics.

First molecular and isotopic evidence of millet processing in prehistoric pottery vessels

“…The results performed on solvent extracts of powdered sherds from these vessels show that a low quantity of miliacin (290 ng g −1 ceramic) is transferred to the pottery vessel wall during cooking of P. miliaceum . No miliacin was detected in the three other millet varieties, confirming previous analysis made directly on the plants28. This study reports yields of 297–476 μg miliacin g −1 P. miliaceum grain following solvent extraction and column chromatography to isolate the neutral fraction28.…”

“…In contrast, a study of pit fills from Neolithic Cishan, China identified miliacin in authentic samples of both P. miliaceum and S. italica and suggested differences between the two species based on the presence of other PTMEs in lower abundance7. The finding of miliacin in S. italica is not supported by investigations of authentic samples28.…”

“…Miliacin is absent in Setaria italica (foxtail millet) and is not ubiquitous in Pennisetum. The strength of this approach is that only a small number of the C4-grasses of the Panicoideae subfamily synthesize miliacin as their sole PTME28. The presence of high abundances of miliacin in sediment profiles indicating the locations of past millet cultivation has already been demonstrated27.…”

“…Other approaches have been explored in order to document the occurrence of millets in the archaeological record. The most promising is molecular analysis of soils and sediments demonstrating associations with millet cultivation in pit fills or sediment cores7272829; although this approach provides little evidence as to how the crop was processed or consumed.…”

“…Miliacin is the principal (c. 99%) PTME in broomcorn millet ( P. miliaceum ) but is absent in many other commonly cultivated species or present in similar abundance to other PTMEs28. It is abundant in other Panicum species but occurs with high abundances of amyrin methyl ethers.…”