Caracterização estrutural e farmacognóstica dos órgãos vegetativos aéreos de três espécies de piper l. (piperaceae): parâmetros de autenticidade e de grau de pureza para o controle de qualidade

Abstract

The purpose this study was to establish authenticity and purity degree parameters for the quality control of Piper arboreum Aubl. var. arboreum, P. callosum Ruiz & Pav. and P. tuberculatum Jacq leaves and stem, plant species of large ethno-medicinal usage, currently being traded as traditional phytotherapeutic products, and with chemical and pharmacological potential to become phytomedicines. Fertile samples of the three Piper species were collected in Belém and Manaus states. The samples were processed and analyzed according to standard methods for light and scanning electron microscopies, histochemistry, energy-dispersive X-ray spectroscopic microanalyses, inductively coupled plasma optical emission spectrometry, and physicochemical determinations, such as moisture, pH, loss on drying, and total, sulphated and acid-insoluble ash. Size, shape, color, texture, fracture surface and transection characteristics, and leaf venation patterns are macroscopic morpho-diagnostic characters to identify the herbal drugs of the studied Piper species when they are not ground or powdered. Leaf callosus emergences in P. callosum and leaf and stem glandular emergences in P. tuberculatum are key-characters to identify the whole herbal drugs of both species. Since medicinal plants and herbal drugs do not differ anatomically, the following characters for the studied Piper species can be used for microscopic morpho-diagnosis purposes of both types raw plant materials: crystal macropatterns; epicuticular wax and cuticular flanges patterns; type and position of the collenchyma; arrangement pattern of the vascular bundles of the petiole; shape in transection of the midrib, leaf margin, petiole, and stem. In addition to these characters are: the occurrence of fibers immediately beneath the epidermis, and arrangement pattern of the vascular bundles in the midrib as well as starch grain morphology in P. callosum; the types of cuticular ornamentation and non-glandular trichomes, arrangement pattern of the stem vascular bundles, and type of hilum of the starch grains in P. arboreum var. arboreum and P. tuberculatum. Acid lipids, essential oils, mixture of essentials and resins, steroids, tannins, and flavonoids are common metabolic compounds for the three Piper species. Terpenoids with carbonyl group and alkaloids were identified only in P. arboreum var. arboreum and P. tuberculatum, respectively. Oleoresins were detected in P. callosum and P. tuberculatum. The moisture, volatile, and total, sulphated and acid-insoluble ash values of the herbals drugs of these species are within the permissible limits. In general, these values were higher in the leaf herbal drugs than in the stem herbal drugs. The metal levels analyzed (aluminum, cadmium, cobalt, chromium, copper, manganese, molybdenum, nickel, lead, tin, vanadium, mercury and arsenic) in the herbal drugs of the studied Piper species are below the toxic levels for human health. The highest metal levels were of aluminum, copper, manganese and vanadium. The structural and pharmacognostical characteristics reported herein for first time for Piper arboreum var. arboreum, P. callosum, and P. tuberculatum should be used as safe parameters of authenticity and purity degree for the quality control of the raw plant materials (i.e. medicinal plants and herbal drugs) of these species.